EXPRESSION OF HLA CLASS II-ASSOCIATED PEPTIDE TRANSPORTER AND PROTEASOME GENES IN HUMAN PLACENTAS AND TROPHOBLAST CELL-LINES

Expression of HLA class I antigens is closely controlled in the placen tal trophoblast cells, which interface directly with maternal cells du ring pregnancy. In this study, the possibility that peptide transporte r (TAP-1, TAP-2) or proteasome (LMP7) genes might be involved in regul ating antigen expression in these or other cells that comprise placent as was investigated. Analysis by Northern blot hybridization showed th at transcripts from all three genes were present in samples of first t rimester and term placental RNA. TAP-1 and TAP-2 messages were consist ently more abundant in early than in late gestation placentas, whereas the reverse was observed for LMP7 mRNA. Further experiments were done on two trophoblast cell lines. One line, Jar, is negative for HLA cla ss I, and the second, JEG-3, expresses HLA-G as well as other HLA clas s I genes. Both Jar and JEG-3 cells contained TAP-1, TAP-2 and LMP7 mR NA. With the exception of LMP7 in JEG-3 cells, message from all three genes was increased by treating the trophoblast cells with interferon- gamma. While no evidence was collected to support the postulate that t he HLA class I negative status of some trophoblast cell subpopulations could be related to absent or dysfunctional TAP-1, TAP-2 or LMP7 mRNA , the data are consistent with the postulate that placental cell expre ssion of HLA class I antigens could be influenced by the availability of peptide transporters and proteasome components.