Analysis of HLA-G expression in malignant hematopoetic cells from leukemia patients.

It has been suggested that HLA-G antigens may provide tumor cells with an effective immune escape mechanism. So far mostly solid tumors have been analyzed; HLA-G antigen was only exceptionally detected. To further examine HLA-G expression, patients were chosen with different forms of leukemia: AML (25), CML (4), ALL (9), CLL (8), HCL (2) and NHL (3). Using flow cytometry with three HLA-G specific mAbs (87G, 01G and MEM-G/9), western blotting with two specific mAbs (4H84 and MEM-G/1) and RT-PCR, neither HLA-G antigen nor mRNA for any HLA-G isoform was detected. These results strongly suggest that HLA-G antigen is not expressed in freshly isolated human leukemia cells and therefore is not involved in their escape from immune attack.