precipitin Any antibody that combines with its specific soluble antigen to form a precipitate. The term is sometimes applied to the precipitate itself. See also agglutination.

precipitin (pri-sip-it-in) n. any antibody that combines with its antigen to form a complex that is seen as a precipitate. The precipitin reaction is a useful means of confirming the identity of an unknown antigen or establishing that a serum contains antibodies to a known disease. See also agglutination.