Microbiology - Antigen Antibody Reaction - Discussion

In equivalent zone, ab and ags are present in optimum conc, as abs are usually divalent and ags are multivalent the cab form bridge between 2 or more ags this linking result in a formation of the multimolecular lattice which makes the reaction visible to the eye.

In the case of post zone and prozone phenomenon, there is no proper linking occur and is less visible to the eye.

In prozone phenomenon at the prozone the Antibodies are in excess and all antigens will bound there will be unbound antibodies, in equivalent zone antibodies and antigens will be at equilibrium and there will maximum bounding hence visible ppt. But in postzone the Antigens will be in excess hence there will unbound Antigens

From the graph between Precipitation and increasing of amount Antigen.

Prozone : Ab>Ag you can see some agglutination.

Equivalent zone : because of the optimal proportion of Ab and Ag you can see maximum and largest lattice caused by ag-ab complex.

Postzone : It's hard to form lattice because low level of ab when compare with ag level.

Because of the antigen antibody complex.