Antibody production stimulating activity of bone marrow cells from tolerant rats

The antibody production stimulating activity of BM cells from SRBC-tolerant and normal rats were studied. Tolerance was induced by repeated injections of SRBC which were begun within 24 h after birth. BM cells obtained from tolerant animals 14-24 days after the last SRBC injection or from normal rats of the same age were used. LN cells from mice immunized with SRBC or BRBC served for the detection of BM activity. Four days after the second injection of antigen, LN cells were removed and cultivated alone or with BM cells from tolerant or control rats for 16 h. After cultivation, immune reaction was estimated by enumeration of indirect PFC. BM cells from SRBC-tolerant rats increased the number of SRBC PFC in the culture more than BM cells from control rats. On the other hand, the stimulatory activity of the BM cells from SRBC-tolerant animals for the BRBC-PFC was lower than that of normal BM cells or it was completely absent. The implications of these findings for the mechanism of the stimulating BM activity are discussed.