Antigen presentation to human T lymphocytes. II. Requirements for Mac-120+ macrophages and responsiveness to interleukin 2.
To investigate mechanisms by which antigen, macrophages, and interleukin 2 (IL2) participate in the induction of secondary T-cell proliferative responses, trinitrophenyl (TNP) was presented in three distinct modes: (i) TNP-modified peripheral blood mononuclear cells (TNP-PBMC), (ii) TNP-PBMC cell sonicates, and (iii) TNP-ovalbumin (TNP-OVA). Stimulators were depleted of Mac-120+ macrophages using Mac-120 monoclonal antibody plus complement. TNP-Mac-120 macrophages stimulated primed T cells nearly as well as TNP-unfractionated macrophages (which were about 40% Mac-120+). In contrast, although greater than 70% DR+, Mac-120- macrophages plus either TNP-OVA or TNP-PBMC sonicate elicited minimal responses compared to unfractionated macrophages plus antigen. After 21-28 days of in vitro priming, macrophage-depleted T cells were not stimulated to proliferate by either IL2 alone or sonicates alone. IL2 plus TNP-PBMC sonicates, however, stimulated significant proliferation. Furthermore, this response was considerably greater than that to IL2 plus either TNP-T cell sonicates or TNP-mouse spleen sonicates. Thus, the Mac-120+ macrophage population may have an important antigen-presenting and/or accessory function in the stimulation of primed T cells by soluble or particulate antigen, although it is unnecessary for responses to intact TNP-Ia+ PBMC. In addition, the data suggest that Ia+ sonicates alone may suffice for induction of IL2 responsiveness, but not for endogenous IL2 production and subsequent proliferation by primed T cells.
D000954:Antigens, Surface / Q000032:analysis; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D006801:Humans; D007376:Interleukin-2 / Q000276:immunology*; D008213:Lymphocyte Activation; D008264:Macrophages / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D014301:Trinitrobenzenes / Q000276:immunology
D000954:Antigens, Surface; D000949:Histocompatibility Antigens Class II; D007376:Interleukin-2; D014301:Trinitrobenzenes