Immunosuppressive alpha globulin from bovine thymus and serum: mode of action upon afferent and efferent arcs of the mouse immune response.

Immunosuppressive bovine alpha globulins of both serum and thymus origin were analyzed for in vitro effects upon the afferent and efferent arcs of the immune system. Although considerable variation in potency occurs between preparations, the functional identity of thymus and serum fractions is apparent. Antigenic recognition and effector capability are not altered whereas the proliferative lymphocyte response is either augmented or suppressed, depending upon the concentration of alpha globulin. A rather selective effect is noted on DNA synthesis and is followed by parallel changes in the development of effector capability, as measured by the development of alloimmune cytotoxic lymphocytes.