Studies on the nonspecific depression of the immune response.

Calf serum has been shown to suppress the primary immune response to erythrocytes and some bacterial antigens in mice if administered prior to and not after immunization. The importance of the route of iniection of antigens and immunosuppressant is indicated. It is suggested that immunosuppression is achieved by phagocytosis and enyzmatic destruction of the injected antigen by peritoneal macrophages. A similar mechanism is probably involved in the type of immunosuppression induced by PHA.