HLA class II induction by interferon-gamma in K562 variant cell line: inhibition by serum lipid.

The induction of class II antigen (Ag) by interferon-gamma (IFN-gamma) in variants of the K562 cell line has been examined in this study. Following incubation of K562A cells with IFN-gamma, surface expression of HLA-DR molecules was demonstrated by indirect immunofluorescence, confirmed by immunoblotting, and HLA-DR3 Ag specificity identified. HLA-DP and HLA-DRW52 Ag were co-expressed, but no HLA-DQ expression occurred. A variant of this line, designated K1A, spontaneously developed resistance to IFN-gamma induction of class II Ag, but continued to express class I Ag. In a third K562 variant, designated K562B, no class II gene products could be induced. Northern blot analysis indicated that mRNA levels correlated with surface class I and II Ag expression in all of the K562 cell lines. Resistance to IFN-gamma inducible class II Ag expression in K1A cells did not involve changes in IFN-gamma receptor affinity or number but was shown to be due to an inhibitory effect of serum lipid. These results indicate that cells derived from a common parental line may differ in susceptibility to a regulatory mechanism affecting IFN-gamma inducible class II Ag expression.