LIPOPOLYSACCHARIDE INTERFERES WITH THE INDUCTION OF PERIPHERAL T-CELLDEATH

In mice injected with superantigens, T cells specific for that antigen proliferate and then die. It has been suggested that the target cells die because they encounter superantigen on the surfaces of nonprofess ional presenting cells, such as B cells, which cannot deliver costimul atory signals to T cells. A number of reagents that induce costimulato ry molecules on B cells were tested. Lipopolysaccharide very effective ly prevented T cell death driven by superantigen. Perhaps surprisingly , the action of lipopolysaccharide was not mediated through the expect ed costimulatory molecule, B7. Rather, the effects of lipopolysacchari de involved the production of inflammatory cytokines, in particular TN F alpha. The rescued cells survived in vitro culture and were resistan t to Pas-induced killing. These data demonstrate that LPS can block an tigen-induced T cell death perhaps by interfering with Fas signaling.