STUDIES ON IMMUNOSUPPRESSIVE PROPERTIES OF A PREGNANCY-ASSOCIATED ALPHA-MACROGLOBULIN

Abstract

A [human] pregnancy-associated serum glycoprotein had an inhibitory effect on several in vitro methods of immunological assessment. This suppressing activity was evident at physiological concentrations and did not appear to be due to cytotoxicity. Transformation induced by agents often regarded as preferential stimulators of T [thymus-derived] lymphocytes (concanavalin A, phytohemagglutinin, allogeneic cells and tuberculin) was significantly depressed by the .alpha.-globulin. This phenomenon was much less evident when lipopolysaccharide or goat anti-human F(ab'')2 serum was employed to selectively stimulate B [bone marrow-derived]-cells. The glycoprotein also blocked antigen-induced inhibition of leukocyte migration, and caused a significant reduction in the number of lymphocytes binding sheep erythrocytes in the spontaneous rosette test. It is proposed that the non-specific inhibitory activity of the .alpha.-macroglobulin probably depends upon some direct effect exerted on the lymphocyte itself and that it is leveled primarily at the cell-mediated immune response.