title: IL-16 inhibition of CD3-dependent lymphocyte activation and proliferation.
abstract: We have recently described the cDNA and predicted protein structure of a natural soluble CD4 ligand, IL-16. IL-16 is chemotactic for CD4+ T cells and induces functional IL-2 receptors in CD4+ T cells. The binding of IL-16 to CD4 results in activation of p56(lck), whose adaptor function is essential for the chemotactic response. Subsequently, increases in intracellular Ca2+ and phosphatidylinositol 1,4,5-trisphosphate occur, as does translocation of protein kinase C from cytosol to membrane. Because of the similarities between these signals and functions and those noted for the CD4 ligand HIV-1 gp120, we investigated the potential regulatory effects of IL-16 on CD3/TCR-mediated lymphocyte activation. Preincubation of human T cells with IL-16 up to 24 h before activation with plate-bound anti-CD3 Abs reduced T cell activation by 80%, as monitored by IL-2R expression and [3H]thymidine uptake. If IL-16 was added following anti-CD3 activation, no suppression was noted. The suppressive effects of preincubation with IL-16 were not rescued by the addition of rIL-2 and were not the result of priming for anti-CD3-induced apoptosis. In addition, IL-16 had no effect on surface expression of CD3 or CD4. However, IL-16 did reduce the magnitude of the anti-CD3-induced intracellular Ca2+ increase. These studies indicate that while the interaction of CD4 with its natural ligand, IL-16, results in Ag-independent chemotaxis and IL-2R expression, this pro-inflammatory state is associated with subsequent transient inhibition of responsiveness via the CD3/TCR complex.
authors.affiliation: The Pulmonary Center, Boston University School of Medicine, MA 02118, USA.
authors.forename: W W
authors.initials: WW
authors.lastname: Cruikshank
authors.forename: K
authors.initials: K
authors.lastname: Lim
authors.forename: A C
authors.initials: AC
authors.lastname: Theodore
authors.forename: J
authors.initials: J
authors.lastname: Cook
authors.forename: G
authors.initials: G
authors.lastname: Fine
authors.forename: P F
authors.initials: PF
authors.lastname: Weller
authors.forename: D M
authors.initials: DM
authors.lastname: Center
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D017252:CD3 Complex / Q000502:physiology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002118:Calcium / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004768:Enterotoxins / Q000276:immunology; D006801:Humans; D019410:Interleukin-16 / Q000502:physiology*; D008213:Lymphocyte Activation / Q000187:drug effects*; D010835:Phytohemagglutinins / Q000494:pharmacology; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D016176:T-Lymphocyte Subsets / Q000276:immunology; D013745:Tetanus Toxoid / Q000276:immunology; D019014:fas Receptor / Q000502:physiology
chemical_list: D017252:CD3 Complex; D004768:Enterotoxins; D019410:Interleukin-16; D010835:Phytohemagglutinins; D015375:Receptors, Interleukin-2; D013745:Tetanus Toxoid; D019014:fas Receptor; C026066:enterotoxin A, Staphylococcal; D002118:Calcium