title: On the mechanism of human T cell suppression.
abstract: Previous evidence from several laboratories suggests that CD8+ T suppressor cells may be important regulatory elements governing specific unresponsiveness of lepromatous lepromatous leprosy patients to M.leprae. To analyse the mechanism of suppression, CD8+ Ts clones were established from lesions and peripheral blood of lepromatous patients and tested for ability to suppress antigen-responsive CD4+. Th clones or PBL. Suppression required induction by specific M.leprae antigen, but was effected in an antigen-non-specific fashion. The Ts clones failed to exhibit cytotoxicity of four antigen-exposed MHC-matched target cells: (i) an ori-SV40 transformed macrophage line; (ii) EBV transformed B cell lines; (iii) primary macrophages; and (iv) M.leprae responsive CD4+ cells. The possibility that Ts clones induce functional inactivation of CD4+ clones in vitro was investigated. M.leprae-responsive CD4+ clones were preincubated with Ts CD8+ clones, APC, and antigen for 16 h, after which the CD8+ cells were removed. The CD4+ clones with M.leprae and APC remained unresponsive to restimulation with APC and antigen for at least 10 days, although they responded to IL-2. Addition of IL-2 to the pre- or post-incubation cultures neither prevented the induction of unresponsiveness, nor reversed it. Earlier models of tolerance have suggested that receptor occupancy in the absence of second signals induces tolerance in B and T cells. Under conditions in which antigen responses of Th clones were HLA-DR-restricted, the Ts clones were able to suppress the response of DR mismatched Th clones. Thus, the effect of the Ts cells, like mechanisms requiring antigen presentation without a second signal, appears to be induction of clonal anergy in Th cells, perhaps by a novel mechanism.
authors.affiliation: Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461.
authors.forename: P
authors.initials: P
authors.lastname: Salgame
authors.forename: R
authors.initials: R
authors.lastname: Modlin
authors.forename: B R
authors.initials: BR
authors.lastname: Bloom
mesh_terms: D000938:Antigen-Presenting Cells / Q000276:immunology; D000942:Antigens, Bacterial; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D015704:CD4 Antigens; D003602:Cytotoxicity, Immunologic; D006684:HLA-DR Antigens; D006801:Humans; D007108:Immune Tolerance; D007376:Interleukin-2 / Q000494:pharmacology; D015440:Leprosy, Lepromatous / Q000276:immunology; D009166:Mycobacterium leprae / Q000276:immunology; D011948:Receptors, Antigen, T-Cell; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
chemical_list: D000942:Antigens, Bacterial; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D015704:CD4 Antigens; D006684:HLA-DR Antigens; D007376:Interleukin-2; D011948:Receptors, Antigen, T-Cell