CHANGES IN MURINE JEJUNAL MORPHOLOGY EVOKED BY THE BACTERIAL SUPERANTIGEN STAPHYLOCOCCUS-AUREUS ENTEROTOXIN-B ARE MEDIATED BY CD4(-CELLS() T)

Bacterial superantigens (SAgs) are potent T-cell stimuli that have bee n implicated in the pathophysiology of autoimmune and inflammatory dis ease. We used Staphylococcus aureus enterotoxin B (SEB) as a model SAg to assess the effects of SAg exposure on gut form and cellularity. BA LB/c, SCID (lacking T cells) and T-cell-reconstituted SCID mice were t reated with SEB (5 or 100 mu g intraperitoneally), and segments of the mid-jejunum were removed 4, 12, or 48 h later and processed for histo chemical or immunocytochemical analysis of gut morphology and major hi stocompatibility complex class II (MHC II) expression add the enumerat ion of CD3(+) T cells and goblet cells. Control mice received saline o nly, SEB treatment of BALB/c mice caused a time- and dose-dependent en teropathy that was characterized by reduced villus height, increased c rypt depth, and a significant increase in MHC II expression. An increa se in the number of CD3(+) T cells was observed 48 h after exposure to 100 mu g of SEB. Enteric structural alterations were not apparent in SEB-treated SCID mice compared to saline-treated SCID mice. In contras t, SEB challenge of SCID mice reconstituted with a mixed lymphocyte po pulation or purified murine CD4(+) T cells resulted in enteric histopa thological changes reminiscent of those observed in SEB-treated BALB/c mice, These findings implicate CD4(+) T cells in this SEB-induced ent eropathy, Our results show that SAg immune activation causes significa nt changes in jejunal villus-crypt architecture and cellularity that a re likely to impact on normal physiological processes. We speculate th at the elevated MHC II expression and increased number of T cells coul d allow for enhanced immune responsiveness to other SAgs or environmen tal antigens.