Suppression of primary immune response by heterologous anti-lymphocyte sera

The effect of anti-lymphocyte serum (ALS) on the primary immune response to sheep erythrocytes (SRBC) in rats was studied by the Jerne Plaque technique. ALS against normal rat lymph node cells, ALS(N) suppressed the immune response to SRBC when administered before the antigen and had no effect on the immune response when administered either with or after the antigen. ALS(I), which was produced against lymph node cells from SRBC immunized rats, produced significant immunosuppression when administered either before or after the antigen.