Mechanism of specific suppression of delayed hypersensitivity response by anti-lymphocyte serum

Mechanism of antigen-specific immunosuppression exhibited by a heterologous anti-rat lymphocyte serum, ALS (CM), was investigated. This ALS possessed antibody activity against T-effector cells responsible for the expression of delayed hypersensitivity (DH) to sheep erythrocytes (SRBC) in rats. Immune lymphocytes were treated in vitro with ALS (CMI) and transferred to inbred recipients. ALS (CMI) inhibited the ability of the immune cells to transfer DH. Prior absorption of ALS (CMI) with gamma-globulin from rat anti-SRBC serum or the immune cells abolished this suppressive ability. These results demonstrated that ALS (CMI) had anti-idiotype activity.