Primary immune response to sheep red blood cells in mice treated with immunoregulatory alpha-globulins (IRA).

Alpha-Globulins from human and bovine sera or from mouse ascitic fluid were separated by ion-exchange chromatography on DEAE-cellulose into fractions A, B, and C. Fractions A and B had no immunosuppressive activity; fraction C injected into mice at the time of antigen administration, but not later, significantly reduced the number of anti-SRBC plaque-forming cells in the spleens of experimental animals. Single high dose inhibited the response better than the same doses given on 4 consecutive days. It is concluded that a critical level of alpha-globulins is necessary to render lymphocytes hyporesponsive, and when once stimulated by antigen they become less susceptible to alpha-globulin action.