title: Evidence for the generation of specific T suppressor lymphocytes by Streptococcus intermedius.
abstract: Crude extracellular products of the Streptococcus intermedius "CEP-Si" were able to strongly decrease the in vitro proliferation of stimulated human peripheral blood mononuclear cells (HPBMC) when evaluated by (3H)-thymidine and (3H)-leucine uptake. On the other hand, CEP-Si only slightly decreased this proliferation when HPBMC were either not stimulated or cultured in poor conditions or immature cells, i.e. thymocytes were used as target instead. Also in vivo CEP-Si was ineffective when target cells were not highly reactive. Both in vivo and in vitro, the effect of CEP-Si was proportional to the time of contact with the target cells. The dynamics of the effects of CEP-Si suggest the generation of "something" ("suppressor cells") which cause an abrupt drop in the values of (3H)-thymidine uptake rather than a progressive decrease of the values, which could indicate a loss effector or helper cells. On the other hand, CEP-Si suppressed the in vitro primary immunization of human HPBMC against SRBC and, furthermore, human HPBMC incubated with CEP-Si were able to suppress the primary immune response against SRBC of, CEP-Si untreated, HPBMC. In some instances of insufficient time of contact of CEP-Si with the target cells, an enhancement of the immune response was observed both in vivo and in vitro. Moreover, the histological pattern of the spleens of C57 BL/6 mice injected with semipurified products of CEP-Si were consistent with an adjuvant-like effect. Finally, the target HPBMC for the semipurified products of CEP-Si acquired the ultrastructural and antigenic characteristics of suppressor T lymphocytes.
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000276:immunology / Q000302:isolation & purification / Q000494:pharmacology*; D000939:Epitopes; D006801:Humans; D007165:Immunosuppression Therapy; D007930:Leucine / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009000:Monocytes / Q000378:metabolism; D013291:Streptococcus / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology; D013936:Thymidine / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D000939:Epitopes; D007930:Leucine; D013936:Thymidine