Practical Applications of Immunology

11. Describe agglutination reactions.
12. Differentiate between direct and indirect agglutination reactions and give examples.
13. Define:
Titer
Microtiter
Seroconversion

Agglutination Reactions

The interaction of particulate antigens (cells that carry antigens) with antibodies leads to agglutination reactions.

Diseases may be diagnosed by combining the patient’s serum with a known antigen.

Diseases can be diagnosed by a rising titer (antibody concentration in serum) or seroconversion (from no antibodies to the presence of antibodies).

Direct Agglutination

Direct agglutination reactions test patient serum for the presence of antibodies against large, cellular antigens.

Direct agglutination reactions can be used to determine antibody titer.

Indirect Agglutination

To test patient serum for the presence of antibodies against soluble antigens serum is mixed with latex spheres with the soluble antigens attached.

Antibodies will then cause visible agglutination of the latex spheres with the soluble antigens attached.

Alternatively, antibodies may be attached to the latex spheres to test for the presence of soluble antigens in patient serum.

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.

Viral hemagglutination occurs when spikes on the virus cause agglutination of red blood cells - there is no antigen-antibody interaction.