Antigen-Antibody Interactions : principles

and Applications

미생물학교실 권 형 주

Strength of Ag-Ab interactions

Ag + Ab Ag-Ab k1

K-1

Affinity: strength of the interaction between an antigen and an antibody Ka : association constant, affinity constant

Determination of antibody affinity by equilibrium dialysis

Ka = [Ab-Ag]/[Ab][Ag]= r

c(n-r)

r= the ratio of the concentration of bound ligandc= the concentration of free ligandn= the number of binding sites per antibody molecule = valency

rc

= Kan-Kar

Scatchard equation

Avidity : the strength of multiple interaction between a multivalent antibody and antigen

Affinity : Low HighAvidity : High LowValence : High Low

IgM IgG

Cross-reactivity

ABO blood-group antigens : antigen (glycolipids) on RBC - Difference in the terminal residues of the sugars Blood group antibodies - elicited by microbial antigens

Streptococcus pyrogenes M protein Ab -- cross-react with myocardinal and skeletal muscle protein - Autoimmune diseases

Vaccines : Cowpox---smallpox express cross-reacting epitopes

Surface Plasmon Resonance (SPR)

Precipitation reactions

Immunoelectrophoresis of an antigen mixture

Agglutination reactions

Hemagglutination

- Hemagglutination is used in blood typing- Bacterial agglutination is used to diagnose infection- Passive agglutination is useful with soluble antigens : Antigen-coated RBC - soluble Ag with RBC treated with tanic acid or chromium chloride

Radioimmunoassay

Enzyme-Linked Immunosorbent Assay (ELISA)

ELISPOT assay Western Blotting

Immunoprecipitation

Immunofluorescence

Flow Cytometry and Fluorescence

Flow Cytometry and Leukemia Typing