ANTIGEN-PROCESSING AND PRESENTATION BY HUMAN TROPHOBLAST-DERIVED CELL-LINES

The trophoblast-derived choriocarcinoma cell lines JEG-3 and JAR expre ss the nonclassical MHC class I molecules HLA-G (JEG-3) or, at a low l evel, HLA-E (JAR), but lack expression of the classical MHC class I mo lecules HLA-A and HLA-B. Expression of these nonclassical MHC class I genes was found to coincide with expression of the genes encoding the peptide transporter associated with Ag processing (TAP). In immunoprec ipitation studies, a physical interaction between the TAP complex and HLA-C or HLA-E could be demonstrated. To investigate whether trophobla st-derived cell lines were capable of peptide processing, transport, a nd loading of MHC class I molecules, HLA-A0201-expressing transfectan ts of JEG-3 and JAR were used for functional studies. These transfecta nts were recognized by both allospecific cytotoxic T cell clones and, after viral infection, by an influenza A matrix peptide-specific cytot oxic T cell clone, indicating that these trophoblast-derived cell line s were capable of presenting endogenously derived peptides in the cont ext of HLA-A0201. From these observations, it can be inferred that th e TAP complex and other molecules involved in Ag processing and presen tation by MHC class I molecules are functionally active in these troph oblast-derived cell lines. This implies that trophoblasts are able to provide antigenic peptides for presentation by nonclassical MHC class I molecules that are naturally expressed by this cell type.