Antigen-Antibody Precipitation Reaction

Study Notes

Precipitation in solution occurs when antibodies react with antigens.
This reaction results in the formation of an antigen-antibody complex that loses its solubility and precipitates.
For the precipitation reaction to occur, the formation of a three-dimensional network is necessary.
The amount of Ag and Ac present must be in an optimal ratio for the formation of the precipitate.
Additional addition of Ag will reduce the amount of precipitate.
The maximum amount of precipitate is obtained when there is a between Ag and Ac the ideal ratio – the equivalence zone.
In cases where there is excess of antibodies, large and soluble complexes are formed.
In cases where there is excess of antigen, a minimal amount of precipitate is formed.
Significant amounts of Ag-Ac complexes are present in the supernatant in cases where antibodies are excess.
Nephelometry is used to quantitate proteins from a solution in which antibodies are present in excess.
IgG, IgA, IgM, complement system factors (C3, C4, factor B), and C-reactive protein all play a role in the precipitation reaction.