Immunosupression of the primary and secondary immune response by an IgM plasmacytoma (TEPC-183).

Previously we had established that TEPC-183 IgM(K) suppressed the primary immune response (IR) to both the T-dependent antigens 2,4-dinitrophenyl-haemocyanin (DNP-HCY) and T-independent pneumococcal polysaccharides. In the current investigation, the effect of TEPC-183 on an ongoing immune response to SS-III and DNP-HCY was examined. It was found that when TEPC-183 was injected 6 days after the initial antigen injection, at the height of the primary IR, the response was significantly suppressed to SS-III and to the DNP ligand. In addition, suppression of the secondary IR occurred when mice were injected with tumour as late as 35 days after the first antigen injection. Tumour removal lifted the immunosuppression to DNP and the tumour-removed group had a similar number of both direct and indirect anti-DNP-PFC, although HA levels were still reduced. When mice were pretreated with serum from normal mice or serum or ascites from TEPC-183 bearing mice, one day prior to and on the day of antigen injection, the immune response to DNP was reduced by TEPC-183 serum but not by normal mouse serum (NMS), while the anti-SSS-III response was reduced by both NMS and TEPC-183 serum. Thus, NMS selectively suppressed the T-independent response, but only TEPC-183 serum suppressed both types of responses. The suppressive effect of serum on the IR of normal mice indicates a role for soluble regulatory suppressive factors present in the serum of normal and tumour-bearing mice. The data are consistent with the idea that the tumour exerts its effect on the inductive as well as the proliferative phase of the immune response.