Secretory component (polymeric immunoglobulin receptor) expression on human keratinocytes by stimulation with interferon-γ and differences in response

Secretory IgA (sIgA) is a major protective factor in the mucosal immune system because of its great ability to form complexes with bacteria. Secretory component (SC) is an 80-kDa glycoprotein, a component of sIgA, which functions as a polymeric immunoglobulin receptor for IgA and aids the secretion of sIgA from the epithelial surface. We studied SC production by keratinocytes which were involved in the inflammatory process using interferon-γ (IFN-γ) as one of the major inflammatory promoters produced by helper T cells. Using two human squamous cell carcinoma cell lines (HSCs) and normal human keratinocytes (NHKs), results from flow cytometric analysis, enzyme-linked immunosorbent assay (ELISA), and Northern blotting revealed that HSCs produced SC when stimulated with IFN-γ, although their responses differed; one line exhibited enhanced SC production whereas the production in the other line was suppressed. NHKs also exhibited SC expression on the cell surface by means of immunocytochemical analysis, flow cytometry and ELISA, however the responses were also different in each strain. Although the reason for the diversity of SC expression on keratinocytes is not clear, these differences may influence epidermal sIgA secretion level.