Modulation of HLA-G expression in human thymic and amniotic epithelial cells

Expression of the nonclassical HLA class I antigen, HLA-G, is tightly regul ated. HLA-G physiologic expression is mostly restricted to some placental a nd thymic cell types. Only few established cell lines express HLA-G in vitr o. Cytokine-induced expression of HLA-G is hardly observed and also depends on the cell lineage. We assessed expression and cytokine regulation of HLA -G in primary cultures derived from human thymus and amnion epithelial cell s, which also express HLA-G in vivo. We show chat HLA-G cell surface expres sion is maintained, but decreases gradually, in primary cultures derived fr om human thymus and amnion epithelial cells. We also show that IFN-gamma re -induces HLA-G cell surface expression and upregulates classical class I ge ne expression in both primary cultures acid in a thymus derived cell line. We further show that IFN-gamma also upregulates levels of HLA-G transcripts in TEC primary cultures. This study provides evidence that IFN-gamma induc tion of HLA-G expression occurs in the human amnion and the thymus, and is mediated ar the transcriptional level in these tissues. These results also suggest a role for the microenvironment in regulating HLA-G in vivo gene ex pression in the thymus and amnion membrane. (C) American Society for Histoc ompatibility and Immunogenetics, 2000. Published by Elsevier Science Inc.