title: Phenotypic and functional properties of murine thymocytes. I. Precursors of cytolytic T lymphocytes and interleukin 2-producing cells are all contained within a subpopulation of "mature" thymocytes as analyzed by monoclonal antibodies and flow microfluorometry.
abstract: The correlation between surface phenotype and function in subpopulations of murine thymocytes has been investigated using flow microfluorometry (FMF). C57BL/6 thymocytes stained with monoclonal antibodies directed against Lyt-2, H-2K(b), and Thy-l.2 and passed on an FACS II flow cytometer could be resolved into at least four distinct subpopulations on the basis of fluorescence and forward light scatter (FLS) measurements. (a) Medium-sized Lyt-2(+) cells that stained strongly with H-2K(b) and weakly with Thy-l.2 (5 percent of total cells); (b) medium-sized Lyt-2(-) cells with other properties as in (a) (10 percent); (c) small Lyt-2(+) cells that stained weakly with H-2K(b) and strongly with Thy-l.2 (60 percent); and (d) large Lyt-2(+) cells that stained weakly with H-2K(b) and very strongly with Thy- 1.2 (23 percent). Cortisone-resistant thymocytes (CRT) were found to correspond phenotypically to populations (a) and (b). The distribution of cytolytic T lymphocyte precursors (CTL-P) directed against H-2(d) alloantigens in subpopulations of C57BL/6 thymocytes that had been sorted according to the phenotypic criteria described above was then investigated. CTL-P in sorted and control populations were quantitated by limiting dilution analysis of mixed leukocyte microcultures established in an excess of interleukin 2 (IL-2). These studies established that all thymus CTL-P could be quantitatively recovered in a subpopulation of cells that was cortisone-resistant, medium-sized, Lyt-2(+), H-2K(b+), and weakly stained with Thy-l.2. In parallel studies, the production of IL-2 by subpopulations of C57BL/6 thymocytes was quantitatively assessed using a recently developed sensitive microassay system. Graded numbers of sorted or control thymocytes were stimulated with irradiated T cell-depleted allogeneic cells and assayed for their ability to support the growth of an IL-2-dependent cytolytic T lymphocyte clone. Using this method, IL-2 production was found to reside entirely in a subpopulation of cortisone-resistant, medium-sized Lyt-2(-) thymocytes. Further phenotypic analysis of this subpopulation of cells indicated that it was homogeneously H-2K(b+) and weakly staining with Thy- 1.2. Taken together with the CTL-P results, these data directly demonstrate that a subpopulation of thymocytes with a mature phenotype (i.e., cortisone- resistant, medium-sized, H-2K(b+), and weakly staining with Thy-l.2) accounts for all the functional activity in the thymus. Reasons for the apparent discrepancy between these results and other recent studies will be discussed.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000950:Antigens, Ly / Q000276:immunology; D000954:Antigens, Surface / Q000276:immunology; D002454:Cell Differentiation; D003348:Cortisone / Q000494:pharmacology; D003602:Cytotoxicity, Immunologic; D005434:Flow Cytometry; D006183:H-2 Antigens / Q000276:immunology; D007376:Interleukin-2 / Q000096:biosynthesis*; D008222:Lymphokines / Q000096:biosynthesis*; D008565:Membrane Proteins / Q000276:immunology; D051379:Mice; D008806:Mice, Inbred AKR; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008811:Mice, Inbred DBA; D010641:Phenotype; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D013601:T-Lymphocytes / Q000145:classification / Q000166:cytology / Q000276:immunology*; D018800:Thy-1 Antigens
chemical_list: D000911:Antibodies, Monoclonal; D000950:Antigens, Ly; D000954:Antigens, Surface; D006183:H-2 Antigens; D007376:Interleukin-2; D008222:Lymphokines; D008565:Membrane Proteins; D018800:Thy-1 Antigens; D003348:Cortisone