∞ generated and posted on 2016.03.20 ∞
In vitro formation of the equivalent of an immune complex.
For precipitation reactions to become visible, sufficient antibody must be present, but not so much that substantial crosslinking between antigen molecules fails to occur.
A variety of serological tests are based upon precipitation reactions. These include the immunodiffusion tests and the precipitin ring test.
Note that agglutination is a similar process to precipitation, but where antigens are associated with whole cells rather than soluble (or colloidal).