title: CTLA-4-B7 interaction is sufficient to costimulate T cell clonal expansion.
abstract: T cell costimulation, particularly by the B7 family members B7-1 and B7-2, plays a critical role in regulating T cell-mediated immunity. Two molecules on T cells, CD28 and CTLA-4, are known to bind to B7. It has been suggested that CD28-B7 interaction promotes T cell response, whereas B7-CTLA-4 interaction downregulates T cell clonal expansion. However, the proposed responses of individual receptors to B7 have not been verified directly. Here, we report that B7-1 promotes clonal expansion of CD28-deficient T cells, and that the CD28-independent costimulatory activity is mediated by CTLA-4, as it is completely blocked by intact and Fab of anti-CTLA-4 mAb. In addition, a mutant B7-1 molecule, B7W88 >A, which has lost binding to CD28 but retained significant CTLA-4 binding activity, promotes T cell clonal expansion. Furthermore, while presence of CD28 enhances T cell response to B7-1, such response is also completely blocked by anti-CTLA-4 mAb. Taken together, our results demonstrate that B7-CTLA-4 interaction promotes T cell clonal expansion, and that optimal T cell response to B7 is achieved when both CD28 and CTLA-4 interact with B7. These results establish an important function of CTLA-4 in promoting T cell activation, and suggest an alternative interpretation of the function of CTLA-4 in T cell activation.
authors.affiliation: Department of Pathology, New York University Medical Center, New York 10016, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Wu
authors.forename: Y
authors.initials: Y
authors.lastname: Guo
authors.forename: A
authors.initials: A
authors.lastname: Huang
authors.forename: P
authors.initials: P
authors.lastname: Zheng
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000069594:Abatacept; D000818:Animals; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D018122:B7-1 Antigen / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D018106:CD28 Antigens / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D016466:CHO Cells; D060908:CTLA-4 Antigen; D006224:Cricetinae; D018796:Immunoconjugates; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009154:Mutation; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D018122:B7-1 Antigen; D018106:CD28 Antigens; D060908:CTLA-4 Antigen; C556707:Ctla4 protein, mouse; D018796:Immunoconjugates; D011993:Recombinant Fusion Proteins; D000069594:Abatacept