An in vivo model for assessing effects of drugs and toxicants on immunocompetence.

An in vivo assessment of the capacity of exposed animals to respond to antigenic challenge is recommended as the first screening phase for detecting potential immunotoxicants, with subsequent in vitro functional tests utilized to pinpoint the site of induced cellular alteration. Risk assessment of a candidate toxicant is based on a comparison of immune profiles of exposed animals with those of animals treated with prototype immunotoxicants. Extrapolation to man is facilitated by the use of licensed vaccines for antigenic challenge and the selection of clinically useful pharmaceutical drugs as prototype immunotoxicants. Three chemically induced alterations in immune responses are presented: 1) Immunosuppression characterized by impaired capacity to produce IgG and IgM classes of antibody on stimulation, 2) chronic high levels of IgE antibody in response to commonly encountered antigens, 3) modification of the capacity to mount an inflammatory response to antigenic material.