RESUMO
The polymeric IgR (pIgR) mediates transcytosis of IgA across epithelial barriers of mucous membranes and exocrine glands. Synthesis of pIgR is up-regulated by the proinflammatory cytokines TNF-alpha, IFN-gamma, and IL-1 in HT-29 human colon carcinoma cells. We previously reported that IFN-gamma and TNF-alpha induce production of the transcription factor IFN regulatory factor-1 (IRF-1) in HT-29 cells and that IRF-1 binds to an element in exon 1 of the PIGR gene. We now report that levels of IRF-1 and pIgR mRNA are coordinately regulated in HT-29 cells by TNF-alpha, IFN-gamma, and IL-1beta. Furthermore, we demonstrate that in vivo expression of pIgR mRNA is greatly depressed in the intestine and liver of IRF-1-deficient mice. Our findings indicate a major role for the IRF-1 transcription factor in regulation of the PIGR gene and suggest a model for regulation of important genes in the mucosal immune system by proinflammatory cytokines.
