The immunization of Wistar rats with 5 mg of chemically modified rat male accessory glands saline extract (MRAG) incorporated into complete Freund's adjuvant (CFA) induced a delayed type hypersensitivity (DTH) response to rat male accessory glands (RAG). Pretreatment with peritoneal cells (PC) obtained from rats 2 h after an intraperitoneal (ip) injection of a partially purified fraction (FI) of RAG (FI-PC2h) suppressed the DTH response to MRAG after immunization with MRAG-CFA, while pretreatment with PC obtained 24 h after an ip injection of FI-RAG (FI-PC24h) induced potentiation of the DTH response to MRAG. 2. The injection of spleen mononuclear cells (SpM), obtained from rats rendered unresponsive to MRAG by pretreatment with FI-PC2h, into normal syngeneic recipients markedly prevented the DTH reaction to MRAG. The transfer of SpM cells from animals injected with FI-PC24h (potentiated animals) to suppressed recipients (recipients of FI-PC2h on days -10 and -3, prior to immunization with MRAG-CFA) showed that SpM cells did not eliminate the suppression state in these recipients, but when they were transferred to normal recipients, they were able to induce a positive response to RAG (P < 0.005). 3. The study of the phenotypic characteristics of the SpM cells prior to transfer showed similar numbers of CD4 and IL-2R SpM cells in both potentiated and normal animals. However, the number of CD8 cells was significantly reduced in SpM cells from potentiated animals compared to that observed in SpM cells from normal animals (P < 0.05).
