The HLA-G monomorphic, nonclassical class I gene encodes the major histocompatibility complex (MHC) molecule, which is the only MHC antigen expressed on cytotrophoblast cells of placenta. In this work, we have investigated expression of the HLA-G gene in fetal tissues and adult peripheral blood cells by using a sensitive hot-start reverse transcriptase PCR technique. PCR amplification with HLA-G primers specific for exon 3 has enabled us to demonstrate an alternatively spliced form of HLA-G mRNA present in fetal first trimester trophoblasts and lacking exon 4 (HLA-G.3-5). This low abundance transcript (approximately 1:200) in comparison to full-length mRNA may encode the protein that excludes the alpha 3 domain and by conformational changes may present a different ability to bind to peptides. Moreover, expression of the HLA-G transcript was found in adult peripheral lymphocytes and equally in B- and T-cell populations. These results are discussed in the context of the fetal-maternal relationship presented by HLA-G gene products.

Kirszenbaum, M., Moreau, P., Gluckman, E., Dausset, J., & Carosella, E. (1994). An alternatively spliced form of HLA-G mRNA in human trophoblasts and evidence for the presence of HLA-G transcript in adult lymphocytes. Proceedings of the National Academy of Sciences, 91(10), 4209–4213.