HLA-G TRANSCRIPTION STUDIES DURING THE DIFFERENT STAGES OF NORMAL ANDMALIGNANT HEMATOPOIESIS (VOL 47, PG 408, 1996)

Specific expression of the non classical class I HLA-G gene on trophob lasts, the only fetal tissue in contact with maternal cells which lack MHC class I antigens, may indicate a role of this gene in fetal-mater nal tolerance. We recently reported HLA-G transcription in peripheral blood leukocytes. In this work, we have investigated HLA-G transcripti on in hematopoietic stem cells, in different hematopoietic lineages an d in malignant cells by using a RT-PCR technique. PCR amplification wi th primers specific to the exon 2 and the 3' untranslated region has e nabled to detect HLA-G transcription in B and T cell populations. No t ranscription was found in CD34+ cells, in thymocytes, in polynuclear c ells, in monocytes and in natural killer cells. Among the malignancies analyzed, HLA-G is transcribed in 2 of 13 cases of acute leukemia cha racterized by a monocytic contingent, in 3 of 6 CLL and in all the cas es of B-NHL (n=6). No HLA-G transcription was detected in myeloma (n=2 ). The splicing type does not seem to be linked to a lymphocyte subpop ulation nor to a malignant proliferation stage. These results suggest that HLA-G is a marker of mature lymphoid cells and may play an immuno logical function as a peptide presenting molecule. HLA-G transcription in some cases of malignancy might indicate a contribution to the tumo ral progression by blocking natural killing reaction.