title: CTLA4-CD80/CD86 interactions on primary mouse CD4+ T cells integrate signal-strength information to modulate activation with Concanavalin A.
abstract: The mechanisms by which concanavalin A (Con A), a lectin, activates T cells are poorly studied. A low dose of Con A is stimulatory for T cells, whereas a high dose of Con A results in suppression of proliferation and enhanced T cell death. The expression and functional roles of costimulatory receptors, CD28 and cytotoxic T-lymphocyte antigen 4 (CTLA4), and their ligands, CD80 and CD86, on primary mouse CD4(+) T cells after activation with different doses of Con A were studied. CTLA4-CD80/CD86 interactions in this T:T cell activation model demonstrate distinct outcomes depending on the dose of Con A. CTLA4-CD80/CD86 interactions inhibit CD4(+) T cell cycling and survival after activation with a suppressive dose of Con A by increasing oxidative stress and decreasing levels of BclX(L). The enhanced CD4(+) T cell death with a suppressive dose of Con A is dependent on excess H(2)O(2) and nitric oxide but is independent of Fas and caspase activity. It is surprising that the increased proliferation of CD4(+) T cells with a suppressive dose of Con A on blocking CTLA4-CD80/CD86 interactions is largely interleukin (IL)-2-independent but is cyclosporine A-sensitive. On activation with a stimulatory dose of Con A, CTLA4-CD80/CD86 interactions enhance T cell activation and survival by reducing the production of reactive oxygen species, increasing IL-2 and BclX(L) levels. Here IL-10 but not transforming growth factor-beta plays a functional role. In summary, CTLA4-CD80/CD86 interactions on T cells integrate signal strength, based on the dose of Con A, to enhance or inhibit primary mouse CD4(+) T cell cycling and survival.
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore.
authors.forename: Sambuddho
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Asma
authors.initials: A
authors.lastname: Ahmed
authors.forename: Dipankar
authors.initials: D
authors.lastname: Nandi
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000187:drug effects / Q000276:immunology*; D000943:Antigens, Differentiation / Q000187:drug effects / Q000276:immunology*; D018122:B7-1 Antigen / Q000276:immunology*; D051940:B7-2 Antigen; D018106:CD28 Antigens / Q000187:drug effects / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D060908:CTLA-4 Antigen; D002453:Cell Cycle / Q000187:drug effects / Q000276:immunology; D016923:Cell Death / Q000187:drug effects / Q000276:immunology; D002470:Cell Survival / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D003208:Concanavalin A / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006861:Hydrogen Peroxide / Q000378:metabolism; D007155:Immunologic Factors / Q000276:immunology; D016753:Interleukin-10 / Q000378:metabolism; D007376:Interleukin-2 / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects* / Q000276:immunology; D008562:Membrane Glycoproteins / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009569:Nitric Oxide / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects / Q000276:immunology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000276:immunology; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D051020:bcl-X Protein
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D018122:B7-1 Antigen; D051940:B7-2 Antigen; C494812:Bcl2l1 protein, mouse; D018106:CD28 Antigens; D060908:CTLA-4 Antigen; C497965:Cd86 protein, mouse; C556707:Ctla4 protein, mouse; D007155:Immunologic Factors; D007376:Interleukin-2; D008562:Membrane Glycoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D003208:Concanavalin A; D016753:Interleukin-10; D009569:Nitric Oxide; D006861:Hydrogen Peroxide