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Chapter 6 Antigen-Antibody Interactions Dr. Capers Kindt • Goldsby • Osborne Kuby IMMUNOLOGY Sixth Edition Chapter 6 Antigen-Antibody Interactions: Principles and Applications Copyright © 2007 by W. H. Freeman and Company Antigen-Antibody (Ag-Ab) Interaction Similar to enzyme-substrate interaction However, does not lead to irreversible chemical alteration in either the antibody or antigen Noncovalent Interactions Hydrogen bonds Ionic bonds Hydrophobic reactions Van der Waals All weak so need combination of all of them to make strong interaction Cross-reactivity Mechanisms of tolerance prevent formation of Abs against one’s own blood group antigens ○ However, exposure to microbial antigens on intestinal bacteria induce formation of Abs, these antigens share similarity to blood group antigens Immunoassays – measuring Ag-Ab interactions Vital roles: ○ Diagnosing disease ○ Monitoring level of humoral response ○ Identifying molecules of biological or medical interest Precipitation Reactions Ag-Ab interactions can form visible precipitate Examples: ○ Radial immunodiffusion ○ Double immunodiffusion ○ immunoelectrophoresis In this example, Anti-dog IgG is Mixed in agar so only what is Placed in wells (Ag) diffuses out In this example, both antibody and antigen diffuse Out of wells Immunoelectrophoresis – Antigen is 1st put into wells, charge is applied to separate components of antigen mixture, then troughs are cut and antibody is allowed to diffuse through gel Agglutination Reactions Visible clumping – agglutination ○ Examples: Hemagglutination Bacterial Agglutination Important in all tests for Antibody to be in right concentation ○ Too much antibody will cause univalent binding, need multivalent for preciptitate or agglutination to occur ELISA Enzyme-Linked Immunosorbent Assay ○ Examples: Indirect ELISA Sandwich ELISA Competitive ELISA Indirect ELISA Used to determine if a particular antibody is present Immunoprecipitation Using microscopic magnetic beads ○ Below is cell with magnetic beads attached Immunofluorescence Using Immunofluorescence to see the effect of cancer treatments E. decrease beta-tubulin III (found in developing neurons, if found in other tissue it can be used as cancer marker) F. decrease thymidilate kinase (needed by tumor cell to repair DNA) Flow Cytometry Can provide quantitative data
