Induction of HLA class I mRNA by cytokines in human fibroblasts: comparison of TNF, IL-1 and IFN-beta.
Expression of HLA class I antigens is known to be regulated by various cytokines at both the mRNA and protein levels. We have examined the induction of HLA-B7 by tumor necrosis factor alpha (TNF), interleukin 1 alpha (IL-1) and interferon beta (IFN-beta) in normal human diploid FS-4 fibroblasts. Optimal induction of HLA-B7 by TNF at 24 h was shown to require a continuous presence of TNF. Since TNF also induces IFN-beta in these cells and the latter cytokine itself has the capacity to upregulate HLA class I expression, we investigated the role of autocrine IFN-beta in the induction of HLA-B7 by TNF. Experiments with neutralizing polyclonal antibodies to recombinant IFN-beta showed that the induction of HLA-B7 mRNA by TNF was partially dependent on autocrine IFN-beta. However, TNF and IFN-beta induced HLA-B7 mRNA with similar kinetics and treatment with saturating concentrations of both TNF and IFN-beta resulted in an additive or possibly synergistic response. The latter findings support the idea that induction of HLA class I by TNF is not mediated solely by autocrine IFN-beta produced in response to TNF. In addition, experiments with the protein synthesis inhibitor cycloheximide suggested that the induction of mRNAs for both the heavy and light (beta 2-microglobulin) chains of the HLA class I antigen by TNF did not require de novo protein synthesis. IL-1 was also shown to increase steady-state mRNA levels of HLA-B7 with kinetics similar to those of TNF and IFN-beta in FS-4 cells.(ABSTRACT TRUNCATED AT 250 WORDS)