title: Phenotypic and functional characterization of human cytolytic T cells lacking expression of CD5.
abstract: Although the CD5 (T1) antigen was initially described as a pan-T cell membrane glycoprotein, we report that 14 of 40 normal individuals were found to have 5% or greater of their blood mononuclear cells characterized as CD3 (T3)+ but CD5- by dual immunofluorescence flow cytometry. These cells expressed normal quantities of surface CD3 and CD2 but low levels of CD7, were CD8+ and CD4-, and CD16-. In order to determine whether cells of this phenotype were functional, six CD5- cytolytic T lymphocyte (CTL) clones isolated from normal individuals were studied. The CD5- CTL clones all demonstrated normal cytolytic activity against appropriate target cells. Monoclonal antibodies (MAbs) directed against CD3, CD8, CD2, and lymphocyte function-associated antigen 3, but not against CD5, inhibited cytolytic activity. Changes in intracellular calcium [( Ca2+]i) in response to anti-CD5 and anti-CD3 MAbs were measured. Stimulation by anti-CD5 MAb alone did not give rise to a change in [Ca2+]i. However, under conditions of limiting concentrations of anti-CD3 MAb, preincubation of normal CD5+, but not CD5-, clones with anti-CD5 MAb led to a dramatic enhancement in the ability of anti-CD3 MAb to elicit a rise in [Ca2+]i. We conclude that CD5- T lymphocytes represent a normal lymphoid phenotype. Although CD5 may be involved in T cell activation when present, these CD5- CTL clones appear to express normal cytolytic activity.
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D000943:Antigens, Differentiation / Q000032:analysis* / Q000276:immunology; D018956:CD5 Antigens; D002118:Calcium / Q000378:metabolism; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006680:HLA Antigens / Q000276:immunology; D006801:Humans; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000276:immunology; D010641:Phenotype; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation; D018956:CD5 Antigens; D006680:HLA Antigens; D008562:Membrane Glycoproteins; D002118:Calcium