In order to better understand the immunological functions of the HLA-G gene, expression of this gene has been studied with RT-PCR in human functional lymphocyte subpopulations. Only one population of cells has not shown any HLA-G mRNA expression, the BY55-mAb-defined natural killer cells in cord blood. This absence of transcription was not modulated by IL2, IFN-gamma or TNF-alpha. Several T clone lymphocytes isolated from human peripheral blood, bone marrow or thymus have shown a significant transcription of the HLA-G gene. Only one clone, with a natural killer phenotype, did not reveal full length or alternatively spliced transcripts of HLA-G. Intensity of HLA-G transcription was not affected by TNF-alpha, IL13 or IL4, but HLA-G transcripts appeared more abundant in the presence than in the absence of IL2.