title: Demonstration of a direct inhibitory effect of cyclosporine on normal human T-cells with two novel models of T-cell activation as probes.
abstract: Two novel models of activation of human peripheral blood quiescent T-cells (T-cells) were utilized herein as probes to analyze the mechanisms and to locate the site of action of cyclosporine (CsA) in the T-cell activation pathway. Highly purified T-cells were activated, independently of accessory cells, with either crosslinked anti-CD2 + anti-CD3 monoclonal antibodies (mAbs) or with sn-1,2-dioctanoylglycerol (DAG) and ionomycin. CsA inhibited the expression of 55-kDa interleukin-2 receptors (IL-2R) and T-cell proliferation in these accessory cell-independent models of T-cell activation. Recombinant IL-2, over a wide range of concentrations that included different binding affinities of cellular receptors for IL-2, did not completely reverse CsA-associated inhibition of IL-2R expression and/or proliferation. In additional experiments, designed to examine early activation related events, CsA did not interfere with the increase in intracellular free calcium concentration initiated with anti-CD2, anti-CD3, anti-CD2 + anti-CD3 mAbs or with ionomycin. DAG-induced and PKC-activation-dependent down-regulation of cell surface expression of CD3 antigens was similarly unaffected by CsA. Our findings unambiguously indicate that CsA has a direct inhibitory effect on T-cells. Moreover, CsA's cellular site of action is distal to calcium mobilization and PKC activation but proximal to IL-2R expression and IL-2-dependent DNA synthesis in normal human T-cells.
authors.affiliation: Laboratory of Immunogenetics and Transplantation, Rogosin Institute, New York, New York.
authors.forename: P
authors.initials: P
authors.lastname: Sehajpal
authors.forename: A
authors.initials: A
authors.lastname: Subramaniam
authors.forename: V K
authors.initials: VK
authors.lastname: Murthi
authors.forename: V K
authors.initials: VK
authors.lastname: Sharma
authors.forename: M
authors.initials: M
authors.lastname: Suthanthiran
mesh_terms: D000945:Antigens, Differentiation, T-Lymphocyte / Q000502:physiology; D017252:CD3 Complex; D002118:Calcium / Q000502:physiology; D003524:Cyclosporins / Q000494:pharmacology*; D004075:Diglycerides / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D008213:Lymphocyte Activation / Q000187:drug effects*; D011493:Protein Kinase C / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects*; D013997:Time Factors
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D003524:Cyclosporins; D004075:Diglycerides; D011948:Receptors, Antigen, T-Cell; D015375:Receptors, Interleukin-2; D011493:Protein Kinase C; D002118:Calcium