Occurrence of two distinct subpopulations of suppressor cells in rats bearing chemically induced tumors.
Spleen cells from rats bearing syngeneic methylcholanthrene-induced sarcomas showed impaired proliferative responses to phytohemagglutinin (PHA) as well as to the KCl tumor extract. Studies were then performed to define suppressor cell systems possibly operating in tumor-bearing rats. For this purpose, thymus and spleen cells from tumor-bearing rats were admixed with tumor-immune or normal rat spleen cells and were assayed for their suppressing activity on proliferative responses of immune spleen cells to the tumor antigens and on those of normal spleen cells to PHA. Anti-rat T cell serum and glass-adherent technique were utilized to characterize the cellular source of suppressor activity in the thymuses and spleens of tumor-bearing rats. The results indicate that there are two distinct subpopulations of suppressor cells in tumor-bearing rats. The first is glass-adherent non-T suppressor cells that inhibit lymphocyte proliferative responses both to the tumor antigens and to PHA. The second is suppressor T cells and can only impair proliferative responses of tumor-immune lymphocytes to the tumor antigens. The former cells were found in tumor-bearers' spleens, while the latter cells were present in their thymuses and spleens. It is suggested from these data that complex mechanisms of immunosuppression are working in tumor-bearing hosts, one of which can be attributed to the existing suppressor cells in those host lymphoid tissues.
D000818:Animals; D002455:Cell Division; D008214:Lymphocytes / Q000473:pathology; D009374:Neoplasms, Experimental / Q000276:immunology* / Q000473:pathology; D010835:Phytohemagglutinins / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013154:Spleen / Q000276:immunology / Q000473:pathology; D013601:T-Lymphocytes / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology
D010835:Phytohemagglutinins