The Immune Response: Antigen-Antibody Reactions. Introduction. Antibodies are bifunctional - they bind to the target antigen they recognize as foreign, and they enable other defense components to react with it Variable domain (Fab) - binds to target antigen
Rapid urine testing for drugs, e.g cocaine – Abuscreen method
Positive pregnancy test
Some viruses bind to RBC and cause hemagglutination. If serum contains anti-viral Abs, then hemagglutination is inhibition – positive test.
Figure 33.11: Tube agglutination test for determining antibody titer.
Figure 33.11: A microtiter plate illustrating hemagglutination. Ab in wells 1-10. Positive control = row 11, negative control = row 12. RBCs added to each well. If enough Ab is available to agglutinate the cells, they bind as a mat to the bottom of the well. If insufficient Ab is available, they form a pellet at the bottom.
Mancini technique – Single radial immunodiffusion assay
Ouchterlony technique – Double diffusion agar assay
- Used to separate major blood proteins in serum for diagnostic tests
Precipitin arcs form where Ab and Ag precipitate.
Figure 33.18 – Immunoprecipitation – Precipitin curve and precipitation ring test.