title: Ly-6A.2 expression regulates antigen-specific CD4+ T cell proliferation and cytokine production.
abstract: Ly-6 proteins appear to serve cell adhesion and cell signaling function, but the precise role of Ly-6A.2 in CD4+ T lymphocytes is still unclear. Overexpression of Ly-6A.2 in T lymphocytes has allowed us to analyze the influence of elevated Ly-6A.2 expression on T cell function. In this study we report reduced proliferation of CD4+ T cells overexpressing Ly-6A.2 in response to a peptide Ag. Moreover, the Ly-6A.2-overexpressing CD4+ cells generated elevated levels of IL-4, a key factor that propels the differentiation of naive CD4+ T cells into Th2 subset. The hyporesponsiveness of Ly-6A.2 transgenic CD4+ T cells is dependent on the interaction of Ly-6A.2 T cells with the APCs and can be reversed by blocking the interaction between Ly-6A.2 and a recently reported candidate ligand. Overexpression of Ly-6A.2 in CD4+ T cells reduced their Ca(2+) responses to TCR stimulation, therefore suggesting effects of Ly-6A.2 signaling on membrane proximal activation events. In contrast to the observed Ag-specific hyporesponsiveness, the Ly-6A.2 transgenic CD4+ T cells produced IL-4 independent of the interactions between Ly-6A.2 and the candidate Ly-6A.2 ligand. Our results suggest that 1) interaction of Ly-6A.2 with a candidate ligand regulates clonal expansion of CD4+ Th cells in response to an Ag (these results also provide further functional evidence for presence of Ly-6A.2 ligand on APC); and 2) Ly-6A.2 expression on CD4+ T cells promotes production of IL-4, a Th2 differentiation factor.
authors.affiliation: Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA.
authors.forename: S Christine
authors.initials: SC
authors.lastname: Henderson
authors.forename: Mihir M
authors.initials: MM
authors.lastname: Kamdar
authors.forename: Anil
authors.initials: A
authors.lastname: Bamezai
mesh_terms: D000818:Animals; D017951:Antigen Presentation; D000938:Antigen-Presenting Cells / Q000276:immunology; D000941:Antigens / Q000276:immunology; D000950:Antigens, Ly / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis*; D015847:Interleukin-4 / Q000096:biosynthesis; D008180:Lupus Erythematosus, Systemic / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D019463:Mice, Inbred MRL lpr; D008822:Mice, Transgenic; D010047:Ovalbumin / Q000276:immunology; D010446:Peptide Fragments / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D013154:Spleen / Q000276:immunology
chemical_list: D000941:Antigens; D000950:Antigens, Ly; D016207:Cytokines; C111390:OVA 323-339; D010446:Peptide Fragments; D011948:Receptors, Antigen, T-Cell; D015847:Interleukin-4; D010047:Ovalbumin; D002118:Calcium