EVIDENCE FOR THE PRESENCE OF THE ALTERNATIVELY SPLICED HLA-G MESSENGER-RNA FORMS IN HUMAN MONONUCLEAR-CELLS FROM PERIPHERAL-BLOOD AND UMBILICAL-CORD BLOOD

The HLA-G monomorphic, nonclassic HLA class I gene encodes the molecul e that is the only major histocompatibility complex antigen expressed on cytotrophoblasts of placenta. This restricted expression on fetal t issue that is in contact with maternal tissue suggests that HLA-G prod ucts may play a role in maternofetal tolerance. We previously have dem onstrated in first-trimester human trophoblasts a new alternatively sp liced form of HLA-G mRNA lacking exon 4 (HLA-G4) and weak expression o f HLA-G1 copy mRNA in adult peripheral blood lymphocytes. By using exo n-specific HLA-G primers, we demonstrate in this work the presence of three additional alternatively spliced forms of HLA-G mRNA in human pe ripheral mononuclear cells (HLA-G2, HLA-G3, and HLA-G4). In umbilical cord blood, HLA-G transcription was observed at very low level and onl y three alternatively spliced forms were detected (HLA-G1, HLA-G2, and HLA-G3). In contrast, we did not revealed any HLA-G transcript in CD3 4(+) fraction of cord blood cells.