Ontogenic and functional implications of the differential expression of HLA-DQ antigens on leukemic cells.

We have examined the HLA class II antigenic profiles on different types of leukemic cells and have attempted to relate these findings to the normal differentiation pathways of the cells from which they have arisen. Monoclonal antibodies reacting with the different HLA class II determinants, HLA-DR, DRw52(MT), and DQ, were used to study the expression of these antigens on Epstein-Barr virus transformed cell lines, chronic lymphocytic leukemic cells, acute lymphoblastic leukemic blasts, acute myeloblastic leukemic blasts, and established leukemic cell lines by indirect immunofluorescence binding and immunoprecipitations. The results showed that whereas the HLA-DR and HLA-DRw52(MT2) antigens are normally expressed on the majority of the cells tested, there is a different expression of the HLA-DQ antigens on acute leukemic blasts, chronic lymphocytic leukemic cells, and leukemic cell lines indicating that the DQ molecules may be differentiation antigens preferentially expressed on mature cells. Furthermore, when the pre-B cell leukemic line NALM 6 was induced to differentiate with phorbol ester (TPA), normal expression of the HLA-DQ antigen was obtained after 5 days of culture. The absence of HLA-DQ antigens from the acute leukemic blasts suggests that these immature cells "froze" in the early stages of cell differentiation. We discuss these findings in relation to the role of these HLA class II antigens in cell differentiation and the immune response.