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Contents

  • Platform Notes and Installation
  • Usage

Features

Accuracy

AutoDock Vina significantly improves the average accuracy of the binding mode predictions compared to AutoDock 4, judging by our tests on the training set used in AutoDock 4 development.[*]

Additionally and independently, AutoDock Vina has been tested against a virtual screening benchmark called the Directory of Useful Decoys by the Watowich group, and was found to be'a strong competitor against the other programs, and at the top of the pack in many cases'. It should be noted that all six of the otherdocking programs, to which it was compared, are distributed commercially.

AutoDock Tools Compatibility

For its input and output, Vina uses the same PDBQT molecular structure file format used by AutoDock. PDBQT files can be generated (interactively or in batch mode) and viewed using MGLTools. Other files, such as the AutoDock and AutoGrid parameter files (GPF, DPF) and grid map files are not needed.


Binding mode prediction accuracy on the test set. 'AutoDock' refers to AutoDock 4, and 'Vina' to AutoDock Vina 1.

Ease of Use

Vina's design philosophy is not to require the user to understand its implementation details, tweak obscure search parameters, cluster results or know advanced algebra (quaternions). All that is required is the structures of the molecules being docked and the specification of the search space including the binding site. Calculating grid maps and assigning atom charges is not needed. The usage summary can be printed with 'vina --help'. The summary automatically remains in sync with the possible usage scenarios.

Implementation Quality

  • By design, the results should not have a statistical bias related to the conformation of the input structure.
  • Attention is paid to checking the syntactic correctness of the input and reporting errors to the user in a lucid manner.
  • The invariance of the covalent bond lengths is automatically verified in the output structures.
  • Vina avoids imposing artificial restrictions, such as the number of atoms in the input, the number of torsions, the size of the search space, the exhaustiveness of the search, etc.

Flexible Side Chains

Like in AutoDock 4, some receptor side chains can be chosen to be treated as flexible during docking.

Speed

AutoDock Vina tends to be faster than AutoDock 4 by orders of magnitude.[*]

Multiple CPUs/Cores

Additionally, Vina can take advantage of multiple CPUs or CPU cores on your system to significantly shorten its running time.

World Community Grid

Qualified projects can run AutoDock Vina calculations for free on the massively parallel World Community Grid.Existing projects using AutoDock Vina there include those targetingAIDS,Malaria,Leishmaniasis andSchistosomiasis.Some of these projects average over 50 years worth of computation per day.


Average time per receptor-ligand pair on the test set.'AutoDock' refers to AutoDock 4, and 'Vina' to AutoDock Vina 1.

License

AutoDock Vina is released under a very permissive Apache license, with few restrictions on commercial or non-commercial use, or on the derivative works.The text of the license can be found here.

Tutorial

If you have never used AutoDock Vina before, please study the Video Tutorial before attempting to use it.

Frequently Asked Questions

How to get started learning to use Vina?

Watching the video tutorial might be the best way to do that.

What is the meaning or significance of the name 'Vina'? Why was it developed?

Please see this mailing list post.

How accurate is AutoDock Vina?Free tiki torch slot machine.

See Features

It should be noted that the predictive accuracy varies a lot depending on the target, so it makes sense to evaluate AutoDock Vina against your particular target first,if you have known actives, or a bound native ligand structure, before ordering compounds. While evaluating any docking engine in a retrospective virtual screen, it might make sense to select decoys of similar size, and perhaps other physical characteristics,to your known actives.

What is the difference between AutoDock Vina and AutoDock 4?

AutoDock 4 (and previous versions) and AutoDock Vina were both developed in the Molecular Graphics Lab atThe Scripps Research Institute. AutoDock Vina inherits some of the ideas and approaches of AutoDock 4, such as treating docking as a stochastic global opimization of the scoring function, precalculating grid maps (Vina does that internally), and some other implementation tricks, such asprecalculating the interaction between every atom type pair at every distance. It also uses the same type of structure format (PDBQT) for maximum compatibility with auxiliary software.

However, the source code, the scoring funcion and the actual algorithms used are brand new,so it's more correct to think of AutoDock Vina as a new 'generation' rather than 'version' of AutoDock. The performance was compared in the original publication [*], and on average, AutoDock Vina didconsiderably better, both in speed and accuracy. However, for any given target, either program may provide a better result, even though AutoDock Vina is more likely to do so.This is due to the fact that the scoring functions are different, and both are inexact.

What is the difference between AutoDock Vina and AutoDock Tools?

AutoDock Tools is a module within the MGL Tools software package specifically for generating input (PDBQT files) forAutoDock or Vina. It can also be used for viewing the results.

Can I dock two proteins with AutoDock Vina?

You might be able to do that, but AutoDock Vina is designed only for receptor-ligand docking. There are better programs for protein-protein docking.

Will Vina run on my 64-bit machine?

Yes. By design, modern 64-bit machines can run 32-bit binaries natively.

Why do I get 'can not open conf.txt' error? The file exists!

Oftentimes, file browsers hide the file extension, so while you think you have a file 'conf.txt', it's actually called 'conf.txt.txt'.This setting can be changed in the control panel or system preferences.

You should also make sure that the file path you are providing is correct with respect to the directory (folder) you are in, e.g. if you are referring simply to conf.txt in the command line, make sure you are in the same directory (folder)as this file. You can use ls or dir commands on Linux/MacOS and Windows, respectively, to list the contentsof your directory.

Why do I get 'usage errors' when I try to follow the video tutorial?

The command line options changed somewhat since the tutorial has been recorded. In particular, '--out' replaced '--all'.

Vina runs well on my machine, but when I run it on my exotic Linux cluster, I get a 'boost thread resource' error. Why?

Your Linux cluster is [inadvertantly] configured in such a way as to disallow spawning threads. Therefore, Vina can not run. Contact your system administrator.

Why is my docked conformation different from what you get in the video tutorial?

The docking algorithm is non-deterministic. Even though with this receptor-ligand pair, the minimum of the scoring function corresponds to the correct conformation,the docking algorithm sometimes fails to find it. Try several times and see for yourself. Note that the probability of failing to find the mininum may be different with a different system.

My docked conformation is the same, but my energies are different from what you get in the video tutorial. Why?

The scoring function has changed since the tutorial was recorded, but only in the part that is independent of the conformation:the ligand-specific penalty for flexibility has changed.

Why do my results look weird in PyMOL?

PDBQT is not a standard molecular structure format. The version of PyMOL used in the tutorial (0.99rc6) happens to display it well (because PDBQT is somewhat similar to PDB).This might not be the case for newer versions of PyMOL.

Any other way to view the results?https://hereyload783.weebly.com/icab-5-8-5-alternative-web-browser.html.

You can also view PDBQT files in PMV (part of MGL Tools), or convert them into a different file format (e.g. using AutoDock Tools, or with 'save as' in PMV)

How big should the search space be?

As small as possible, but not smaller. The smaller the search space, the easier it is for the docking algorithm to explore it.On the other hand, it will not explore ligand and flexible side chain atom positions outside the search space. You should probably avoid search spaces bigger than 30 x 30 x 30 Angstrom, unless you also increase '--exhaustiveness'.

Why am I seeing a warning about the search space volume being over 27000 Angstrom^3?

This is probably because you intended to specify the search space sizes in 'grid points' (0.375 Angstrom), as in AutoDock 4.The AutoDock Vina search space sizes are given in Angstroms instead. If you really intended to use an unusuallylarge search space, you can ignore this warning, but note that the search algorithm's job may be harder.You may need to increase the value of the exhaustiveness to make up for it. This will lead to longer run time.

The bound conformation looks reasonable, except for the hydrogens. Why?

AutoDock Vina actually uses a united-atom scoring function, i.e. one that involves only the heavy atoms.Therefore, the positions of the hydrogens in the output are arbitrary.The hydrogens in the input file are used to decide which atoms can be hydrogen bond donors or acceptors though,so the correct protonation of the input structures is still important.

What does 'exhaustiveness' really control, under the hood?

In the current implementation, the docking calculation consists of a number of independent runs, starting from random conformations.Each of these runs consists of a number of sequential steps. Each step involves a random perturbation of the conformation followedby a local optimization (using the Broyden-Fletcher-Goldfarb-Shanno algorithm) and a selection in which the step is either accepted or not. Each local optimization involves many evaluations of the scoring function as well asits derivatives in the position-orientation-torsions coordinates.The number of evaluations in a local optimization is guided by convergence and other criteria.The number of steps in a run is determined heuristically, depending on the size and flexibility of the ligand and the flexible side chains. However, the number of runs is set by the exhaustiveness parameter. Since the individual runs are executed in parallel, where appropriate, exhaustiveness also limits the parallelism.Unlike in AutoDock 4, in AutoDock Vina, each run can produce several results: promising intermediate results are remembered.These are merged, refined, clustered and sorted automatically to produce the final result.

Why do I not get the correct bound conformation?

It can be any of a number of things:

  • If you are coming from AutoDock 4, a very common mistake is to specify the search space in 'points' (0.375 Angstrom), instead of Angstroms.
  • Your ligand or receptor might not have been correctly protonated.
  • Bad luck (the search algorithm could have found the correct conformation with good probability, but was simply unlucky). Try again with a different seed.
  • The minimum of the scoring function correponds to the correct conformation, but the search algorithm has trouble finding it. In this case, higher exhaustiveness or smaller search space should help.
  • The minimum of the scoring function simply is not where the correct conformation is. Trying over and over again will not help, but may occasionally give the right answer if two wrongs (inexact search and scoring) make a right. Docking is an approximate approach.
  • Related to the above, the culprit may also be the quality of the X-ray or NMR receptor structure.
  • If you are not doing redocking, i.e. using the correct induced fit shape of the receptor, perhaps the induced fit effects are large enough to affect the outcome of the docking experiment.
  • The rings can only be rigid during docking. Perhaps they have the wrong conformation, affecting the outcome.
  • You are using a 2D (flat) ligand as input.
  • The actual bound conformation of the ligand may occasionally be different from what the X-ray or NMR structure shows.
  • Other problems

How can I tweak the scoring function?

You can change the weights easily, by specifying them in the configuration file,or in the command line. For example

doubles the strenth of all hydrogen bonds.

Functionality that would allow the users to create new atom and pseudo-atom types,and specify their own interaction functions is planned for the future.

This should make it easier to adapt the scoring function to specific targets,model covalent docking and macro-cycle flexibility,experiment with new scoring functions,and, using pseudo-atoms, create directional interaction models.

Stay tuned to the AutoDock mailing list, if you wish to be notified of any beta-test releases.

Why don't I get as many binding modes as I specify with '--num_modes'?

This option specifies the maximum number of binding modes to output. The docking algorithm may find fewer 'interesting' binding modes internally.The number of binding modes in the output is also limited by the 'energy_range', which you may want to increase.

Why don't the results change when I change the partial charges?

AutoDock Vina ignores the user-supplied partial charges. It has its own way of dealing with the electrostatic interactions through the hydrophobic andthe hydrogen bonding terms. See the original publication [*] for details of the scoring function.

I changed something, and now the docking results are different. Why?

Firstly, had you not changed anything, some results could have been different anyway, due to the non-deterministic nature of the search algorithm.Exact reproducibility can be assured by supplying the same random seed to both calculations, but only if all other inputs and parameters are the same as well. Even minor changes to the input can have an effect similar to a new random seed.What does make sense discussing arethe statistical properties of the calculations:e.g. 'with the new protonation state, Vina is much less likely to find the correct docked conformation'.

How do I use flexible side chains?

You split the receptor into two parts: rigid and flexible, with the latter represented somewhat similarly to how the ligand is represented. See the section 'Flexible Receptor PDBQT Files' of the AutoDock4.2 User Guide (page 14) for how to do thisin AutoDock Tools.Then, you can issue this command: vina --config conf --receptor rigid.pdbqt --flex side_chains.pdbqt --ligand ligand.pdbqt.Also see this write-up on this subject.

How do I do virtual screening?

Please see the relevant section of the manual.

Please note that a variety of docking management applications exist to assist you in this task.

I don't have sufficient computing resources to run a virtual screen. What are my options?

You may be able to run your project on the World Community Grid, or use DrugDiscovery@TACC. See Other Software.

I have ideas for new features and other suggestions.

For proposed new features,we like there to be a wide consensus,resulting from a public discussion,regarding their necessity.Please consider starting or joining a discussion on the AutoDock mailing list.

Will you answer my questions about Vina if I email or call you?

No. Vina is community-supported. There is no obligation on the authors to help others with their projects.Please see this page for how to get help.

Platform Notes and Installation

Windows

Artificial Immunity Mac OS

Compatibility

Vina is expected to work on Windows XP and newer systems.

Installing

Double-click the downloaded MSI file and follow the instructions

Running

Open the Command Prompt and, if you installed Vina in the default location, typeIf you are using Cygwin, the above command would instead beSee the Video Tutorial for details.Don't forget to check out Other Software for GUIs, etc.

Linux

Compatibility

Vina is expected to work on x86 and compatible 64-bit Linux systems.

Installing

Optionally, you can copy the binary files where you want.

Running

If the executable is in your PATH, you can just type 'vina --help' instead.See the Video Tutorial for details.Don't forget to check out Other Software for GUIs, etc.

Mac

Compatibility

The 64 bit version is expected to work on Mac OS X 10.15 (Catalina) and newer.The 32 bit version of Vina is expected to work on Mac OS X from 10.4 (Tiger) through 10.14 (Mojave).

Installing

Optionally, you can copy the binary files where you want.

Running

If the executable is in your PATH, you can just type 'vina --help' instead.See the Video Tutorial for details.Don't forget to check out Other Software for GUIs, etc.

Building from Source

Attention: Building Vina from source is NOT meant to be done by regular users!(these instructions might be outdated)

Step 1: Install a C++ compiler suite

On Windows, you may want to install Visual Studio; on OS X, Xcode; and on Linux, the GCC compiler suite.

Step 2: Install Boost

Install Boost.(Version 1.41.0 was used to compile the official binaries. With other versions, your luck may vary)Then, build and run one of the example programs, such as the Regex example, to confirm that you have completed this step. If you can't do this, please seek help from the Boost community.

Step 3: Build Vina

If you are using Visual Studio, you may want to create three projects: lib, main and split, with the source code from the appropriate subdirectories. lib must be a library, that the other projects depend on, and main and split must beconsole applications. For optimal performance, remember to compile using the Release mode.

On OS X and Linux, you may want to navigate to the appropriate build subdirectory, customize the Makefileby setting the paths and the Boost version, and then type Lord of the rings slot machine strategy.

Other Software

Disclaimer: This list is for information purposes only and does not constitute an endorsement.
  • Tools specifically designed for use with AutoDock Vina (in no particular order):
    • MGLTools, which includes AutoDock Tools (ADT) and Python Molecular Viewer (PMV). ADT is required for generating input files for AutoDock Vina, and PMV can be used for viewing the results
    • PyRx can be used to set up docking and virtual screening with AutoDock Vina and to view the results
    • The new Autodock/Vina plugin for PyMOL can be used to set up docking and virtual screening with AutoDock Vina and to view the results
    • Computer-Aided Drug-Design Platform using PyMOL is another plugin for PyMOL that also integrates AMBER, Reduce and SLIDE.
    • AutoGrow uses AutoDock Vina in its rational drug design procedure
    • NNScore will re-score Vina results using an artificial neural network trained on Binding MOAD and PDBBind
    • A Vina GUI layer for Windows by Biochem Lab Solutions can be used to facilitate virtual screening with AutoDock Vina
    • VSDK can be used to faciliate virtual screening with AutoDock Vina
    • PaDEL-ADV can be used to facilitate virtual screening with AutoDock Vina
    • DrugDiscovery@TACC allows you to do virtual screening with AutoDock Vina through their web site
    • NBCR CADD Pipeline provides access to virtual screening with AutoDock Vina on NBCR computers
    • MOLA is a bootable, self-configuring system for virtual screening using AutoDock4/Vina on computer clusters
    • SMINA is a modification of Vina that links with OpenBabel for I/O and supports additional tweaks of the scoring function
    • Off-Target Pipeline is a platform intended to carry out secondary target identification and docking
    • AUDocker can be used to facilitate virtual screening with AutoDock Vina
    • World Community Grid can be used by qualified projects to run AutoDock Vina calculations for free on the massively parallel network of computers, where volunteers donate their idle CPU time.
    • DockoMatic is a graphical user interface intended to facilitate virtual screening with AutoDock and AutoDock Vina.
    • VinaLC is a modification of Vina by the Lawrence Livermore National Laboratory that takes advantage of MPI on computer clusters
  • Other tools that you are likely to find useful while docking or virtual screening with AutoDock Vina:
    • PyMOL is one of the most popular programs for molecular visualization and can be used for viewing the docking results
    • OpenBabel can be used to convert among various structure file formats, assign the protonation states, etc.
    • ChemAxon Marvin can be used to visualize structures, convert among various structure file formats, assign the protonation states, etc.

Usage

Summary

The usage summary can be obtained with 'vina --help':

Configuration file

For convenience, some command line options can be placed into a configuration file.

For example:

In case of a conflict, the command line option takes precedence over the configuration file one.

Search space

The search space effectively restricts where the movable atoms, including those in the flexible side chains, should lie.

Exhaustiveness

With the default (or any given) setting of exhaustiveness, the time spent on the search is already varied heuristically depending on the number of atoms, flexibility, etc. Normally, it does not make sense to spend extra time searching to reduce the probability of not finding the global minimum of the scoring function beyond what is significantly lower than the probability that the minimum is far from the native conformation.However, if you feel that the automatic trade-off made between exhaustiveness and time is inadequate, you can increase the exhaustiveness level. This should increase the time linearly and decrease the probability of not finding the minimum exponentially.

Output

Energy

The predicted binding affinity is in kcal/mol.

RMSD

RMSD values are calculated relative to the best mode and use only movable heavy atoms. Two variants of RMSD metrics are provided, rmsd/lb (RMSD lower bound) and rmsd/ub (RMSD upper bound), differing in how the atoms are matched in the distance calculation:
  • rmsd/ub matches each atom in one conformation with itself in the other conformation, ignoring any symmetry
  • rmsd' matches each atom in one conformation with the closest atom of the same element type in the other conformation (rmsd' can not be used directly, because it is not symmetric)
  • rmsd/lb is defined as follows:rmsd/lb(c1, c2) = max(rmsd'(c1, c2), rmsd'(c2, c1))

Hydrogen positions

Vina uses a united-atom scoring function. As in AutoDock, polar hydrogens are needed in the input structures to correctly type heavy atoms as hydrogen bond donors. However, in Vina, the degrees of freedom that only move hydrogens, such as the hydroxyl group torsions, are degenerate. Therefore, in the output, some hydrogen atoms can be expected to be positioned randomly (but consistent with the covalent structure). For a united-atom treatment, this is essentially a cosmetic issue.

Separate models

All predicted binding modes, including the positions of the flexible side chains are placed into one multimodel PDBQT filespecified by the 'out' parameter or chosen by default, based on the ligand file name. If needed, this file can be splitinto individual models using a separate program called 'vina_split', included in the distribution.

Advanced Options

AutoDock Vina's 'advanced options' are intended to be primarily used by people interested in methods development rather thanthe end users. The usage summary including the advanced options can be shown with

The advanced options allow

  • scoring without minimization
  • performing local optimization only
  • randomizing the input with no search (this is useful for testing docking software)
  • changing the weights from their default values (see the paper[*] for what the weights mean)
  • displaying the individual contributions to the intermolecular score, before weighting (these are shown with '--score_only'; see the paper[2] for what the terms are)

Virtual Screening

You may want to choose some of the tools listed under Other Software to perform virtual screening. Alternatively, if you are familiar with shell scripting, you can do virtual screening without them.

The examples below assume that Bash is your shell. They will need to be adapted to your specific needs.

Windows

To perform virtual screening on Windows, you can either use Cygwin and the Bash scripts below, or, alternatively, adapt them for the Windows scripting language.

Linux, Mac

Suppose you are in a directory containing your receptor receptor.pdbqt and a set of ligands named ligand_01.pdbqt, ligand_02.pdbqt, etc.

You can create a configuration file conf.txt, such as

and dock all ligands with this shell script.The script assumes that vina is in your PATH.Otherwise, modify it accordingly.

PBS Cluster

If you have a Linux Beowulf cluster,you can perform the individual dockings in parallel.

Continuing with our example, instead of executing all the dockings in a loop locally,we will write one *.job script per ligand,and use qsub (a PBS command)to schedule these scripts to be executed by the cluster.

Run this shell script to do it.The script assumes that vina and qsub are in your PATH.Otherwise, modify it accordingly.

Once the jobs have been scheduled, you can monitor their status with

Selecting Best Results

If you are on Unix and in a directory that contains directories with PDBQT files, all of which are AutoDock Vina results,you may find this Python script useful for selecting the top results. Run it as:

to get the file names of the top 10 hits, which can then be easily copied.

History

Brief summaries of changes between versions can be foundhere.

Citation

If you used AutoDock Vina in your work, please cite:
O. Trott, A. J. Olson,AutoDock Vina: improving the speed and accuracy of docking with a new scoring function, efficient optimization and multithreading,Journal of Computational Chemistry 31 (2010) 455-461

Getting Help

Please seethis pageif you have questions about AutoDock Vina.

Reporting Bugs

Potential bug reports are greatly appreciated, even if you are not exactly sure that they are bugs.However, please do not include requests for assistance along with your bug report.See this pageinsead.

Likely bugs:

  • Early termination
  • Failure to terminate
  • Changes of the covalent lengths or of the invariant angles in the output
  • 'Obviously wrong' clashes (check your 'search space' though)
  • Disagreement with the documentation

Likely not bugs:

  • Anything that happens before you run Vina or after it finished
  • Occasional disagreement with the experiment
  • Vina's refusal to open a file that does not exist (e.g. try ls conf.txt to see if the file is really there)

Reporting

You can send your reports to the AutoDock mailing list. Please remember to provide a descriptive 'Subject' line and all of the information needed to reproduce the problem you are seeing.(redirected from artificial active immunity)
Also found in: Dictionary, Thesaurus, Encyclopedia.
Related to artificial active immunity: artificial passive immunity

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[ĭ-mu´nĭ-te] the condition of being immune; the protection against infectious disease conferred either by the immune response generated by immunization or previous infection or by other nonimmunologic factors. It encompasses the capacity to distinguish foreign material from self, and to neutralize, eliminate, or metabolize that which is foreign (nonself) by the physiologic mechanisms of the immune response.
The mechanisms of immunity are essentially concerned with the body's ability to recognize and dispose of substances which it interprets as foreign and harmful to its well-being. When such a substance enters the body, complex chemical and mechanical activities are set into motion to defend and protect the body's cells and tissues. The foreign substance, usually a protein, is called an antigen, that is, one that generates the production of an antagonist. The most common response to the antigen is the production of antibody. The antigen--antibody reaction is an essential component of the overall immune response. A second type of activity, cellular response, is also an essential component.
The various and complex mechanisms of immunity are basic to the body's ability to protect itself against specific infectious agents and parasites, to accept or reject cells and tissues from other individuals, as in blood transfusions and organ transplants, and to protect against cancer, as when the immune system recognizes malignant cells as not-self and destroys them.
There has been extensive research into the body's ability to differentiate between cells, organisms, and other substances that are self (not alien to the body), and those that are nonself and therefore must be eliminated. A major motivating force behind these research efforts has been the need for more information about growth and proliferation of malignant cells, the inability of certain individuals to develop normal immunological responses (as in immunodeficiency conditions), and mechanisms of failure of the body to recognize its own tissues (as in autoimmune diseases).Immunological Responses. Immunological responses in humans can be divided into two broad categories: humoral immunity, which takes place in the body fluids (humors) and is concerned with antibody and complement activities; and cell-mediatedArtificial Immunity Mac OS or cellular immunity, which involves a variety of activities designed to destroy or at least contain cells that are recognized by the body as alien and harmful. Both types of responses are instigated by lymphocytes that originate in the bone marrow as stem cells and later are converted into mature cells having specific properties and functions.
The two kinds of lymphocytes that are important to establishment of immunity are T lymphocytes (T cells) and B lymphocytes (B cells). (See under lymphocyte.) The T lymphocytes differentiate in the thymus and are therefore called thymus-dependent. There are several types involved in cell-mediated immunity, delayed hypersensitivity, production of lymphokines, and the regulation of the immune response of other T and B cells.
The B lymphocytes are so named because they were first identified during research studies involving the immunologic activity of the bursa of Fabricius, a lymphoid organ in the chicken. (Humans have no analogous organ.) They mature into plasma cells that are primarily responsible for forming antibodies, thereby providing humoral immunity.
Humoral Immunity. At the time a substance enters the body and is interpreted as foreign, antibodies are released from plasma cells and enter the body fluids where they can react with the specific antigens for which they were formed. This release of antibodies is stimulated by antigen-specific groups (clones) of B lymphocytes. Each B lymphocyte has IgM immunoglobulin receptors that play a major role in capturing its specific antigen and in launching production of the immunoglobulins (which are antibodies) that are capable of neutralizing and destroying that particular type of antigen.
Most of the B lymphocytes activated by the presence of their specific antigen become plasma cells, which then synthesize and export antibodies. The activated B lymphocytes that do not become plasma cells continue to reside as “memory” cells in the lymphoid tissue, where they stand ready for future encounters with antigens that may enter the body. It is these memory cells that provide continued immunity after initial exposure to the antigens.
There are two types of humoral immune response: primary and secondary. The primary response begins immediately after the initial contact with an antigen; the resulting antibody appears 48 to 72 hours later. The antibodies produced during this primary response are predominantly of the IgM class of immunoglobulins.
A secondary response occurs within 24 to 48 hours. This reaction produces large quantities of immunoglobulins that are predominantly of the IgG class. The secondary response persists much longer than the primary response and is the result of repeated contact with the antigens. This phenomenon is the basic principle underlying consecutive immunizations.
The ability of the antibody to bind with or “stick to” antigen renders it capable of destroying the antigen in a number of ways; for example, agglutination and opsonization. Antibody also “fixes” or activates complement, which is the second component of the humoral immune system. Complement is the name given a complex series of enzymatic proteins which are present but inactive in normal serum. When complement fixation takes place, the antigen, antibody, and complement become bound together. The cell membrane of the antigen (which usually is a bacterial cell) then ruptures, resulting in dissolution of the antigen cell and a leakage of its substance into the body fluids. This destructive process is called lysis.
Cellular Immunity. This type of immune response is dependent upon T lymphocytes, which are primarily concerned with a delayed type of immune response. Examples of this include rejection of transplanted organs, defense against slowly developing bacterial diseases that result from intracellular infections, delayed hypersensitivity reactions, certain autoimmune diseases, some allergic reactions, and recognition and rejection of self cells undergoing alteration, for example, those infected with viruses, and cancer cells that have tumor-specific antigens on their surfaces. These responses are called cell-mediated immune responses.
The T lymphocyte becomes sensitized by its first contact with a specific antigen. Subsequent exposure to the antigen stimulates a host of chemical and mechanical activities, all designed to either destroy or inactivate the offending antigen. Some of the sensitized T lymphocytes combine with the antigen to deactivate it, while others set about to destroy the invading organism by direct invasion or the release of chemical factors. These chemical factors, through their influence on macrophages and unsensitized lymphocytes, enhance the effectiveness of the immune response.
Among the more active chemical factors are lymphokines, which are potent and biologically active proteins; their names are often descriptive of their functions: Ones that directly affect the macrophages are the macrophage chemotactic factor, which attracts macrophages to the invasion site; migration inhibitory factor, which causes macrophages to remain at the invasion site; and macrophage-activating factor, which stimulates the metabolic activities of these large cells and thereby improves their ability to ingest the foreign invaders.
Another factor, a protein called interferon, is produced by the body cells, especially T lymphocytes, following viral infection or in response to a wide variety of inducers, such as certain nonviral infectious agents and synthetic polymers.
A portion of the population of T lymphocytes is transformed into killer cells by the lymphocyte-transforming factor (blastogenic factor). These activated lymphocytes produce a lymphotoxin or cytotoxin that damages the cell membranes of the antigens, causing them to rupture.
In order to ensure an ample supply of T lymphocytes, two factors are at work: lymphocyte-transforming factor stimulates lymphocytes that have already undergone conversion to sensitized T lymphocytes, so that they increase their numbers by repeated cell division and clone formation; in the absence of antigens, transfer factor takes over the task of sensitizing those lymphocytes that have not been exposed to antigen.
It is apparent that the immune response brings about intensive activity at the site of invasion; it is not only the pathogen that is destroyed, but invariably, there is death or damage to some normal tissues.
Interactions Between the Two Systems. There are several areas in which the cellular and humoral systems interact and thereby improve the efficiency of the overall immune response. For example, a by-product of the enzymatic activity of the complement system acts as a chemotactic factor, attracting T lymphocytes and macrophages to the invasion site. In another example, although T lymphocytes are not required for the production of antibody, there is optimal antibody production after interaction between T and B lymphocytes.
For a discussion of abnormalities of the immune response system, see immune response.
Types of Immunity. An individual may be naturally immune to certain pathological conditions or may acquire immunity through either active or passive means.
Natural immunity is a genetic characteristic of an individual and is due to the particular species and race to which one belongs, to one's sex, and to one's individual ability to produce immune bodies. All humans are immune to certain diseases that affect animals of the lower species; males are more resistant to some disorders than are females, and vice versa. Persons of one race are more susceptible to some diseases than those of another race that has had exposure to the infectious agents through successive generations. One's individual ability to produce immune bodies, and thereby ward off pathogens, is influenced by one's state of physical health, one's nutritional status, and one's emotional response to stress.
In order for an individual to acquire immunity one's body must be stimulated to produce its own immune response components (active immunity) or these substances must be produced by other persons or animals and then passed on to the person (passive immunity). Active immunity can be established in two ways: by having the disease or by receiving modified pathogens and toxins. When an individual is exposed to a disease and the pathogenic organisms enter the body, the production of antibody is initiated. After recovery from the illness, memory cells remain in the body and stand ready as a defense against future invasion. It is possible, through the use of vaccines, bacterins, and modified toxins (toxoids), to stimulate the production of specific antibodies without having an attack of the disease. These are artificial means by which an individual can acquire active immunity.
Sometimes it is desirable to provide “ready-made” immune bodies, as in cases in which the patient has already been exposed to the antigen, is experiencing the symptoms of the disease, and needs reinforcements to help mitigate its harmful effects. Examples of conditions for which an individual may be given such passive immunity include tetanus, diphtheria, and a venomous snake bite. The patient is given immune serum, which contains gamma globulin, antibodies (including antitoxin) produced by the animal from which the serum was taken.
It is not always necessary that the patient actually suffer from the disease and exhibit its symptoms before passive immunity is provided. In some instances in which exposure to an infectious agent is suspected, immune bodies may be given to ward off a full-blown attack or at least to lessen its severity.
Another way in which immunity can be passively acquired is across the placental barrier from fetus to mother. The maternal antibody thus acquired serves as protection for the newborn until he can actively establish immunity on his own. Although humoral immunity can be acquired in this way, cellular immunity cannot.
acquired immunity specific immunity attributable to the presence of antibody and to a heightened reactivity of antibody-forming cells, specifically immune lymphoid cells (responsible for cell-mediated immunity), and of phagocytic cells, following prior exposure to an infectious agent or its antigens, or passive transfer of antibody or immune lymphoid cells (adoptive immunity).
adoptive immunity passive immunity of the cell-mediated type conferred by the administration of sensitized lymphocytes from an immune donor.
artificial immunity acquired (active or passive) immunity produced by deliberate exposure to an antigen, such as a vaccine.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

ac·quired im·mu·ni·ty

resistance resulting from previous exposure of an individual in question to an infectious agent or antigen; it may be active and specific, as a result of naturally acquired (apparent or inapparent) infection or intentional vaccination (artificial active immunity); or it may be passive, being acquired through transfer of antibodies from another person or from an animal, either naturally, as from mother to fetus, or by intentional inoculation (artificial passive immunity).

Artificial Immunity Mac Os X

acquired immunity

n.
Immunity obtained either from the development of antibodies in response to exposure to an antigen, as from vaccination or an attack of an infectious disease, or from the transmission of antibodies, as from mother to fetus through the placenta or the injection of antiserum.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

acquired immunity

Artificial Immunity Mac Os Catalina

(1) Any immune response to exogenous antigens.
(2) Any compromise in immune function unrelated to inherited defects in the immune system.
(3) Immunity in which non-self antigens trigger an anti-self immune reaction after a period of sensitisation. Foreign antigens are then “attacked” by sensitised T cells, which are responsible for the so-called cellular immunity; plasma cells, B cells and other specialised immune cells act in concert with T cells to produce antibodies, the humoral immune response, which attach to the antigen, directing T-cell activity; antibodies also stimulate the release of nonspecific chemical mediators (e.g., complement, IFN, ILs), which enhance antigen destruction.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

acquired immunity

Immunology
1. Adaptive immunity Any immune response to exogenous antigens or immunogens.
2. Secondary immunity Any compromise in immune function unrelated to inherited defects in the immune system. See AIDS.
3. Immunity in which non-self antigens trigger an antiself immune reaction after a sensitization period.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

ac·quired im·mu·ni·ty

(ă-kwīrd' i-myū'ni-tē)
Resistance resulting from previous exposure of the individual in question to an infectious agent or antigen; it may be active, as a result of naturally acquired infection or vaccination; or passive, being acquired from transfer of antibodies from another person or from an animal, either from mother to fetus or by inoculation.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

ac·quired im·mu·ni·ty

(ă-kwīrd' i-myū'ni-tē)
Resistance due to previous exposure of the individual in question to an infectious agent or antigen; may be active, due to naturally acquired infection or vaccination; or passive, acquired from transfer of antibodies from another person or animal, either from mother to fetus or by inoculation.
Medical Dictionary for the Dental Professions © Farlex 2012

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