AGGLUTINATION REACTION

Khadija Batool 2206M010

AGGLUTINATION REACTION

When a particulate antigen is mixed with its antibody in the presence of electrolytes at a suitable temperature and pH, the particles are clumped or agglutinated due to lattice formation. Agglutination reaction is more sensitive than precipitation reactions for the detection of antibodies. The same principles govern agglutination and precipitation. Incomplete or monovalent antibodies do not cause agglutination, though they combine with the antigen. They may act as blocking antibodies, inhibiting agglutination by the complete antibody added subsequently.

Excess of antibody leads to prozone and excess of antigen leads to postzone phenomenon.
Types of agglutination:-

1. SLIDE AGGLUTINATION:-
a. Drop of antiserum + a drop of uniform suspension of antigen clump formation
b. Control is a must
c. Visible to the naked eye
d. Uses - blood grouping , serotyping of bacteria

2. TUBE AGGLUTINATION:-
a. Standard quantitative method for the measurement of antibodies
b. Uses WIDAL TEST for typhoid fever
c. Heterophile agglutination test : Weil-Felix
d. Haemagglutination- RBCs are used as antigens
e. Example Paul - Bunell test , Cold agglutination test

3. PASSIVE AGGLUTINATION:-
a. Soluble antigens are attached to the surface of the carrier particles to convert precipitation tests into agglutination tests.
b. More convenient and sensitive
c. Carrier particles-RBCs , Latex, Bentonite
d. Example-ASO test