HLA-G CLASS-I GENE-EXPRESSION IN NORMAL AND MALIGNANT HEMATOPOIETIC-CELLS

The class Ib HLA-G gene encodes for a molecule which is selectively ex pressed in fetal placental cells. Fetomaternal tolerance could be part ially explained by the interactions between HLA-G molecules and KIR re ceptors of decidual NK cells. To determine whether the presence of HLA -G antigens might constitute a factor of immune tolerance during the t umoral process, we compared the expression of the HLA-G gene in normal and malignant hematopoietic cells. Despite a HLA-G transcriptional ac tivity in several lymphocytes and monocytes, no antigens are found at the cell surface or in the cytosol using the specific HLA-G mAb, 87G. This lack of expression does not appear modified in malignant hematopo ietic cells. However, treatment of the monohistiocytic cell line U937 with different cytokines enabled the expression of HLA-G antigens to b e induced. We suggest that the potential induction of HLA-G molecules in monocytic malignant cells following secretion of cytokines may cons titute a factor of immune tolerance in patients. Human Immunology 59, 524-528 (1998). (C) American Society for Histocompatibility and Immuno genetics, 1998. Published by Elsevier Science Inc.