Practical Applications of Immunology

 

 

Vaccines

 

1. Edward Jenner developed the modern practice of vaccination when he      inoculated people with cowpox virus to protect them against small pox.

 

Principles And Effects Of Vaccination

 

1. Herd immunity results when most of a population is immune to a disease.

 

Types Of Vaccines And Their Characteristics

 

1. Attenuated whole-agent vaccines consist of attenuated (weakened)
2. Microorganisms: attenuated virus vaccines generally provide lifelong immunity.
3. Inactivated whole-agent vaccines consist of killed bacteria or viruses.
4. Toxoids are inactivated toxins.
5. Subunit vaccines consist of antigenic fragments of a microorganism; these include recombinant vaccines and acellular vaccines.
6. Conjugated vaccines combine the desired antigen with a protein that boosts the immune response.
7. Nucleic acid vaccines, or DNA vaccines, are being developed.  These cause the recipient to make the antigenic protein associated with class I MHC.

 

The Development Of New Vaccines

 

1. Viruses for vaccines may be grown in animals, cell cultures, or chick embryos.
2. Recombinant vaccines and nucleic acid vaccines do not need to be grown in cells or animals.
3. Genetically engineered plants may someday provide edible vaccines.
4. Adjuvants improve the effectiveness of some antigens.

 

Safety Of Vaccines

 

1. Vaccines are the safest and most effective means of controlling infectious diseases.

 

 

Diagnostic Immunology

 

1. Many tests based on the interactions of antibodies and antigens have been developed to determine the presence of antibodies or antigens in a patient.

 

 

 

Precipitation Reactions

 

1. The interaction of soluble antigens with IgG or IgM antibodies leads to precipitation reactions.
2. Precipitation reactions depend on the formation of lattices and occur best when antigen and antibody are present in optimal proportions.  Excesses of either component decrease lattice formation and subsequent precipitation.
3. The precipitin ring test is performed in a small tube.
4. Immunodiffusion procedures are precipitation reactions carried out in an agar gel medium.
5. Immunoelectrophoresis conbines electrophoresis with immunodiffusion for the analysis of serum proteins.

 

Agglutination Reactions

 

1. The interaction of particulate antigens (cells that carry antigens) with antibodies leads to agglutination reactions.
2. Diseases may be diagnosed by combining the patient’s serum with a known antigen.
3. Diseases can be diagnosed by a rising titer or seroconversion (from no antibodies to the presence of antibodies).
4. Direct agglutination reactions can be used to determine antibody titer.
5. Antibodies cause visible agglutination of soluble antigens affixed to latex spheres in indirect or passive agglutination tests.
6. Hemagglutination reactions involve agglutination reactions using red blood cells.  Hemagglutination reactions are used in blood typing, the diagnosis of certain diseases, and the identification of viruses.

 

Neutralization Reactions

 

1. In neutralization reactions, the harmful effects of a bacterial exotoxin or virus are eliminated by a specific antibody.
2. An antitoxin is an antibody produced in response to a bacterial exotoxin or a toxoid that neutralizes the exotoxin.
3. In a virus neutralization test, the presence of antibodies against a virus can be detected by the antibodies’ ability to prevent cytopathic effects of viruses in cell cultures.
4. Antibodies against certain viruses can be detected by their ability to interfere with viral hemagglutination in viral hemagglutination inhibition tests.

 

Complement-Fixation Reactions

 

1. Complement-fixation reactions are serological tests based on the depletion of a fixed amount of complement in the presence of an antigen- antibody reaction.

 

Fluorescent-Antibody Techniques

 

1. Fluorescent-antibody techniques use antibodies labeled with fluorescent dyes.
2. Direct fluorescent-antibody tests are used to identify specific microorganisms.
3. Indirect fluorescent-antibody tests are used to demonstrate the presence of antibody in serum.
4. A fluorescence-activated cell sorter can be used to detect and count cells labeled with fluorescent antibodies.

 

Enzyme-Linked Immunosorbent Assay (ELISA)

 

1. ELISA techniques use antibodies linked to an enzyme, such as horseradish
2. peroxidase or alkaline phosphatase.
3. Antigen – antibody reactions are detected by enzyme activity.  If the indicator enzyme is present in the test well, an antigen-antibody reaction has occurred.
4. The direct ELISA is used to detect antigens against a specific antibody bound in a test well.
5. The indirect ELISA is used to detect antibodies against an antigen bound in a test well.

 

Radioimmunoassay

 

1. In RIA, antibodies against the compound are combined with a radioactively labeled antigen and a sample containing an unknown amount of antigen.
2. Analysis of radioactivity in the resulting antigen-antibody complexes indicates the amount of antigen in the sample.

 

The Future Of Diagnostic Immunology

 

1.  The use of monoclonal antibodies will continue to make new diagnostic tests possible.