Antibody and assays Methods for measuring antigen-antibody reactions haye been well established and include those that have direct biologic relevance Table 1). The combination of Ab with biologically active Ag(virus, toxin, enzyme and hormone) can be detected by neutralization of the virus infection, toxicity, enzymatic and hormone activity, respectively. Precipitation and agglutination have also been adapted fo development of several useful assaysMethods for measuring antigen-antibody reactions have been well established and include those that have direct biologic relevance (Table 1). The combination of Ab with biologically active Ag (virus, toxin, enzyme and hormone) can be detected by neutralization of the virus infection, toxicity, enzymatic and hormone activity, respectively. Precipitation and agglutination have also been adapted fo development of several useful assays. Antibody and assays