Stimulation via the CD43 coreceptor augments T cell proliferation during the early phase of antigen-induced activation

R2/60 is a monoclonal antibody (mAb) that recognizes the murine CD43 molecule expressed on mature T cells, developing thymocytes, and a subset of bone marrow hematopoietic stem cells. Recent studies using R2/60 demonstrate that CD43 is a costimulatory receptor involved in the activation of murine T cells. In the present study we have examined the kinetics of CD43-mediated costimulation in murine T cell populations including purified CD4⁺ and CD8⁺ peripheral T cells, and T cells activated in antigen-induced mixed-lymphocyte cultures. In each population, CD43 stimulation significantly enhanced T cell proliferation compared to non-CD43 activated cultures. CD43 costimulation was greatest in conjunction with suboptimal CD3 stimulation, and was most efficient during the early phase of antigen-driven activation, suggesting that under normal biologic conditions the role of CD43 may be to augment T cell responses early in immune activation.