ADMINISTRATION TO MOUSE OF ENDOTOXIN FROM GRAM-NEGATIVE BACTERIA LEADS TO ACTIVATION AND APOPTOSIS OF T-LYMPHOCYTES

Lipopolysaccharide (LPS) from gramnegative bacteria is a well-known T cell-independent B lymphocyte mitogen and macrophage/monocyte activato r. While the conventional view holds that LPS is ignored by T cells, w e report here that administration of LPS to mice activates all B cells , but also engages most CD4 and CD8 T cells, as measured by the expres sion of the activation markers CD69 and CD25 and by size increase. T c ells recruited in endotoxin-treated mice showed, following in vitro st imulation by concanavalin A, altered patterns of cytokine production. In vivo, massive T cell apoptosis was evidenced in the days following LPS exposure. The present observation may contribute novel insights in to the mechanisms of endotoxin shock and of the immunological conseque nces of gram-negative infections.