Abstract
Retroviral superantigens such as minor lymphocyte stimulating (Mls) antigen play an important role in the pathogenesis of acute graft-versus-host disease (GVHD). However, it remains unclear how exogenous bacterial superantigens modulate acute GVHD. In this study, we tested the effects of staphylococcal enterotoxin B (SEB) on the development of acute GVHD in a model involving the systemic transfer of parental C57Bl/6 spleen cells into BDF1 mice. SEB treatment suppressed the expansion of donor-derived T cells and blocked the decrease in the number of host cells. Impaired haematopoiesis was actually rescued by treatment with SEB. In SEB-treated mice, both spontaneous proliferation and IL-2 production in T cells were suppressed on day 2 after parental cell infusion. On day 21, the number of donor-derived CD4+ Vbeta8+ T cells markedly decreased in the spleen of SEB-treated mice. Donor-derived CD4+ T cells failed to proliferate in response to host alloantigens, and both donor- and host-derived T cells were unable to produce IL-2 in response to concanavalin A stimulation, suggesting that SEB treatment induced a general immunosuppressive state. Our results indicate that SEB treatment prevents the development of acute GVHD by leading to unresponsiveness of donor-derived T cells against host alloantigens in a Vbeta-restricted and unrestricted manner.