Transforming growth factor-beta enhances secretory component and major histocompatibility complex class I antigen expression on rat IEC-6 intestinal epithelial cells.

Transforming growth factor-beta (TGF-beta) has been implicated as having a role in inflammatory responses by inducing cellular infiltration and the release of inflammatory cytokines. In this study, the IEC-6 rat intestinal epithelial cell line was used as a model to assess the effect of TGF-beta 1 on the expression of various plasma membrane determinants. TGF-beta 1 induced a dose-dependent increase in the percentage of cells expressing surface secretory component (SC) and class I major histocompatibility (MHC) antigens. However, the expression of class II MHC was unaffected. In contrast, epidermal growth factor had no effect on any of the surface proteins studied. The TGF-beta 1-enhanced expression of SC was accompanied by an enhanced binding of polymeric, but not monomeric, immunoglobulin A (IgA). Preincubation of the TGF-beta 1-treated cells with an anti-human beta-galactosyltransferase (beta-GT) antiserum did not block the binding of the anti-SC antibody, indicating that the TGF-beta-induced increase in SC staining was due to SC expression and not the polymeric immunoglobulin-binding enzyme, beta-GT. These results indicate that TGF-beta 1 may be important in immune functions involving intestinal epithelial cells by enhancing the expression of surface class I MHC antigens and SC, a protein responsible for the transport of polymeric IgA into the intestinal lumen.