HLA-G MESSENGER-RNA FORMS IN HUMAN TROPHOBLASTS AND PERIPHERAL-BLOOD LYMPHOCYTES - POTENTIAL USE IN PRENATAL-DIAGNOSIS

HLA-G limited polymorphic gene maps to the human major histocompatibil ity complex (MHC) class I subregion and encodes the molecule which is the only MHC class I antigen expressed on cytotrophoblast cells at the maternal-fetal interface. In this tissue, HLA-G primary mRNA is diffe rentially spliced. We have used a sensitive hot start reverse transcri ptase-polymerase chain reaction (RT-PCR) technique to investigate the expression of HLA-G gene in first trimester trophoblasts and adult per ipheral blood cells. PCR amplification with HLA-G primers specific of exon 3 has enabled us to demonstrate a novel alternatively spliced for m of HLA-G mRNA present in fetal first trimester trophoblasts and lack ing exon 4 (HLA-G4). Cloning the whole PCR product and hybridizing rec ombinant bacterial colonies with specific probes has permitted evaluat ion of HLA-G4 vs. full length mRNA frequency at similar to 1:200. More over, the presence of HLA-G transcripts was found at a very weak level in adult peripheral blood lymphocytes and equally in B- and T-cell po pulations. These results are relevant in the context of immune toleran ce and in the potential use of HLA-G transcripts as a marker for RT-PC R detection of tile fetal cells in maternal blood.