Differential expression and interferon response of HLA class I genes in thymocyte lines and response variants

cDNA clones which seem to represent the alleles of HLA-A and -B expressed by the thymoma MOLT-4 have been isolated and used as locus-specific probes to measure the corresponding mRNA levels in MOLT-4 and other human thymocyte lines, and the effect of interferon (IFN)-alpha and -gamma on these levels. It is shown in MOLT-4, and in its derived line YHHH, that HLA-B mRNA levels are undetectable before treatment but respond to IFN-alpha and -gamma more markedly than those of HLA-A. This differential induction is best shown with YHHH, which is hypersensitive to IFN-alpha, where the HLA-B mRNA levels increase to a level threefold those of HLA-A. Other thymocyte lines tested also showed preferential induction by IFN-alpha of HLA-B, although the basal levels of HLA-A and -B tended to be similar. The effect of the altered ratio of HLA-A to -B mRNA on surface expression of the antigens and the correlation between basal level expression and inducibility are discussed.