Constitutive expression of 4-1BB on T cells enhances CD4+ T cell responses

Abstract

4-1BB, a transmembrane molecule, member of the tumor necrosis factor receptor superfamily, is an im portant costim ulatory molecule in the immune response, plays a key role in the clonal expansion and survival of CD8+ T cells. In this study, we investigated 4-1BB regulation of CD4+ T cell responses using 4-1BB transgenic (TG) mice that constitutively expressed 4-1BB on mature T cells. We first showed that CD4+ T cells of 4-1BB TG mice had more sustained proliferative capacity in response to TCR/4-1BB stimulation in vitro compared to WT mice. Secondly, 4-1BB TG mice exhibited a more elevated contact hypersensitivity (CHS) response mediated by CD4+ Th1 cells due to more vigorous expansion of and apoptotic inhibition of CD4+ T cells. Finally, CD4+ T cells of 4-1BB TG mice had a heightened capacity for T cell prim ing. Overall, our results demonstrate the involvement of 4-1BB in CD4+ Th1 cell responses by regulating the clonal expansion and survival of CD4+ T cells as seen in CD8+ T cells.