HLA class-I and class-II antigen expression by human leukemic K562 cells and by Burkitt-K562 hybrids: modulation by differentiation inducers and interferon.

K562 cells, which could be regarded as pluripotent hematopoietic progenitors, are usually considered as HLA class-I and class-II-negative cells. We show here that differentiation induction (with either sodium butyrate, 12-O-tetradecanoyl-phorbol-13-acetate, or teleocidin) or recombinant alpha- or gamma-interferon (IFN) treatment resulted in the augmentation of HLA class-I antigen expression. This augmentation of HLA class-I antigens was also observed in the Burkitt X K562 hybrid cells PUTKO and DUTKO (the latter coming from two presumably HLA-A, B-negative parents). HLA class-I genes are thus functional in K562 cells. In this system, alpha- and gamma-IFN had no clear differentiating capacity, since they were not able to modulate the expression of various hematopoietic markers, as chemical differentiation inducers did. On the other hand, neither differentiation induction nor interferon treatment could induce HLA class-II antigen expression on K562 cells. These molecules could be very faintly induced in PUTKO and DUTKO hybrids, in contrast with strong HLA class-II expression on the B parental lines. Whether these results are due to "lineage infidelity" in K562 cells or whether K562 cells represent the proliferation of HLA class-I-positive class-II-negative hematopoietic cells, with active suppression of HLA class-II antigen expression, is discussed.