Enhancement of monocyte class I and II histocompatibility antigen expression in man by in vivo beta-interferon.

Changes in monocyte cell-surface markers were assessed during treatment of patients with beta-interferon (beta-IFN). Immediately after isolation monocytes were analysed using monoclonal antibodies and flow cytometry. After 2 days of beta-IFN significant increases in major histocompatibility complex (MHC) related cell-surface products were observed while no changes in Leu-M3, a non-MHC associated monocyte-specific marker, were found. The most striking increases were (1) the percent of monocytes positive for HLA-DQ (mean increase = 19.7%); (2) the relative amount of monocyte-surface HLA-DR (mean increase = 10.1 mean fluorescence intensity (MFI) units); and (3) the relative amount of monocyte-surface beta 2-microglobulin (mean increase = 7.7 MFI units). Increases in MHC expression over baseline were greater after 2 days of beta-IFN treatment than after 14 days of IFN. Thus beta-IFN, produced by recombinant DNA technology and purified to homogeneity, increased surface MHC expression on monocytes in vivo. Additionally, levels of 2-5A synthetase, a type-I IFN-induced enzyme, were significantly increased in patient peripheral blood mononuclear cells after treatment. Increases in 2-5A synthetase were found to correlate with increases in MHC expression suggesting a common mechanism for induction. Flow cytometry can in the future be used to correlate changes in MHC expression with therapeutic response.