T lymphocyte infiltration is a prominent feature of the skin inflammation associated with infections by toxin (superantigen)-secreting Staphylococcus aureus or Streptococcus bacteria. The cutaneous lymphocyte-associated antigen (CLA) has been hypothesized to be a homing receptor (HR) involved in selective migration of memory/effector T cells to the skin. Since the expression of this putative skin-selective HR is known to be under strict microenvironmental control, we sought to determine the effect of staphylococcal and streptococcal toxins on T cell expression of CLA. After in vitro stimulation of peripheral blood mononuclear cells with staphylococcal enterotoxin B, toxic shock syndrome toxin-1, and streptococcal pyrogenic exotoxins A and C, there was a significant increase in the numbers of CLA+ T cell blasts (p < 0.01), but not blasts bearing the mucosa-associated adhesion molecule alpha e beta 7-integrin, compared with T cells stimulated with phytohemaglutinin (PHA) or anti-CD3. Bacterial toxins were also found to specifically induce interleukin (IL) 12 production. More importantly, induction of toxin-induced CLA expression was blocked by anti-IL-12, and the addition of IL-12 to PHA-stimulated T cells induced CLA, but not alpha e beta 7-integrin, expression. These data suggest that bacterial toxins induce the expansion of skin-homing CLA+ T cells in an IL-12-dependent manner, and thus may contribute to the development of skin rashes in superantigen-mediated diseases.

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