Monoclonal antibody 2D10 recognizes a novel T cell costimulatory molecule on activated murine B lymphocytes.
We have developed a panel of rat mAbs against dibutyryl cAMP-activated 5C2 cells. In this panel, one mAb, 1G10, recognized murine B7. Another mAb designated 2D10 did not bind to murine B7 but could recognize a surface molecule expressed only on dibutyryl cAMP-activated 5C2 mouse B lymphoma cells or on LPS-stimulated splenic B cells. This new molecule is referred to as early T cell costimulatory molecule-1 (ETC-1). From both activated 5C2 cells and splenic B cells, mAb 2D10 immunoprecipitated a 59- to 60-kDa protein, which was different from the 47- to 55-kDa murine B7 protein precipitated from the same cell populations. FACS analysis showed that, in contrast to B7, the expression of ETC-1 on 5C2 cells was induced by lower concentrations of dibutyryl cAMP and displayed a faster kinetics. LPS-stimulated splenic B cells expressed relatively low levels of B7 and much higher levels of ETC-1. Importantly, in an Ag presentation assay using activated 5C2 cells as APC, the secretion of IL-2 by C8A3 T hybrids was partially inhibited by mAb 2D10 alone and completely blocked by combination use of mAbs 2D10 and 1G10 in a dose-dependent and synergistic fashion. In a one-way primary MLR, mAb 2D10 alone at 0.1 to 1 microgram/ml inhibited T cell proliferation by 19 to 56%. However, an additive blocking effect (up to 76%) was observed when two mAbs were added in combination. Thus, our data have demonstrated that a novel T cell costimulatory molecule is present on activated murine B cells, which, in cooperation with B7, may play a critical role in optimal T cell activation.
Chen
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Department of Inflammation and Autoimmune Diseases, Roche Research Center, Nutley, NJ 07110.
Faherty
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Gault
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Connaughton
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Powers
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Godfrey
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Nabavi
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D000818:Animals; D000911:Antibodies, Monoclonal; D017951:Antigen Presentation; D000961:Antilymphocyte Serum; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D018122:B7-1 Antigen / Q000302:isolation & purification; D003994:Bucladesine / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D008211:Lymphocyte Cooperation / Q000276:immunology; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D013601:T-Lymphocytes / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000961:Antilymphocyte Serum; D018122:B7-1 Antigen; D008070:Lipopolysaccharides; D003994:Bucladesine