Vβ Specificity of Superantigen TSST-1 Plus CD28 Costimulation Without APCs

Abstract

Little has so far been known about the role of antigen-presenting cells (APCs) in the activation of T cells by superantigens. Recently several studies showed that superantigens could directly activate purified T cells in the presence of CD28 costimulation. Here we investigate Vβ expression of T cells activated by the superantigen toxic shock syndrome toxin-1 (TSST-1), plus CD28 costimulation, in the absence of APCs. The aim of this study was to ask if TSST-1 activated purified T cells in the presence of CD28 costimulation with the same specificity as in the presence of APCs. We provide evidence that the specificity of TSST-1 to human Vβ, in the presence of CD28 costimulation, is identical to that in the presence of APCs, with Vβ2 being significantly expanded. The results indicate that the main role of APCs in the superantigen-mediated T cell activation may be to provide T cells with CD28 costimulation.