SECRETORY COMPONENT (POLYMERIC IMMUNOGLOBULIN RECEPTOR) AS AN INTRINSIC INHIBITOR OF BIOLOGICAL FUNCTIONS OF INTERFERON-GAMMA IN KERATINOCYTES

Secretory component (SC) acts as a trans-membrane polymeric immunoglob ulin receptor of epithelial cells and is known to bind to polymeric Ig A. and to contribute to the secretion of secretory IgA (sIgA), We desc ribe a new biological function for free SC (FSC) by which the expressi on of intercellular adhesion molecule-1 (ICAM-1) and HLA-DR induced by interferon gamma (IFN gamma) is inhibited in human keratinocytes. Thi s activity coincided with suppression of adenosine cyclic 3,5-monophos phate (cyclic AMP) production in keratinocytes. Keratinocytes produced SC after stimulation with IFN gamma and this production was suppresse d by the addition of H-7 or propranolol, The addition of propranolol r esulted in prolongation of ICAM-1 expression on keratinocytes induced by IFN gamma. These results suggest that endogenously produced SC, as well as exogenously added FSC, acts as an inhibitor of IFN gamma. Ther efore, our results suggest that SC plays an antiinflammatory role in t he pathogenesis of inflammatory skin diseases via inhibition in kerati nocytes of IFN gamma induced expression of ICAM-1 and HLA-DR.