In normal human epidermis, expression of HLA-DR antigen is restricted to Langerhans cells (LC) and acrosyringial epithelium. However, in diseases such as lichen planus and graft-vs.-host, HLA-DR antigen appears to be expressed by keratinocytes, although the exact source of the HLA-DR is unclear. Two possibilities are that (1) the HLA-DR is shed by neighboring immunocompetent cells, or (2) that the keratinocytes are synthesizing the antigen themselves. Recently, gamma interferon has been shown to induce HLA-DR biosynthesis and expression on human malignant melanoma cells lines and on normal vascular endothelium. We report here that pure recombinant human gamma interferon (100 units/ml) induces HLA-DR expression on 60-70% of cultured human adult keratinocytes depleted of LC within 2-4 days of culture as determined by fluorescence-activated cell sorter (FACS) analysis using monoclonal antibodies. No residual LC or lymphocytes could be detected in these cultures. This is the first demonstration of HLA-DR expression by cultured human keratinocytes. This expression may be of functional significance in antigen presentation and cell-mediated cytotoxicity involving the epidermis.

Recombinant gamma interferon induces class II antigen (HLA-DR) biosynthesis and expression on normal cultured human keratinocytes. HLA-DR expression was not induced on keratinocytes by recombinant alpha or beta interferons in a similar dose range nor by Con A or PHA. HLA-DR (L243) expression, as determined by FACS analysis, was detected as early as 1-2 days after addition of r-IFN-gamma to the cultures and was maximal after 4-8 days. Keratinocytes were analyzed for expression of another class II antigen, HLA-DC (Leu-10). Little or no expression of Leu-10 (DC) was detectable on these cells although Fc receptors for the IgG1 isotype were increased. These data indicate a unique role for gamma interferon in the differential regulation of keratinocyte class II antigen biosynthesis and expression. Induction of HLA-DR on keratinocytes may be functionally important in expanding the number of antigen presenting cells in the skin for the induction of an immune response and/or targeting these keratinocytes for cytolysis.

We report that human leukocyte interferon preparations increase the expression of 82-microglobulin by 100-200% on the surface of normal fibroblast and melanoma cell lines sensitive to interferon. This increase in expression can be correlated with an increase in HLA synthesis as measured by incorporation of [3S]methionine in these antigens. This enhanced HLA synthesis, which is 5-to 17-fold, is time dependent and dose related. Synchronized cells in the GO/GI phase of the cell cycle appear to be more sensitive to this interferon action. Neither an increase in surface expression nor in HLA synthesis is observed in a melanoma cell line resistant to the antiviral and antigrowth effects of interferon. Furthermore, there appears to be a stronger correlation between this increased HLA synthesis and the antiviral function than between it and the antiproliferative action of interferon.Interferons are glycoproteins that have antiviral, immunoregulatory, and antiproliferative functions. Previously, human leukocyte interferon has been shown to enhance the expression of surface major histocompatibility antigens, HLA-A and -B and f32-microglobulin, a low molecular weight subunit of HLA. This increased expression has been noted in normal human peripheral blood lymphocytes and lymphoblastoid cells lines (1-4) and murine lymphoid systems (5-7) by absorption studies, fluorescence intensity of labeled antibodies as detected by the fluorescence-activated cell sorter, and radioimmunoassay. The increase of HLA appears to be specific in that other lymphocyte surface markers, such as immunoglobulin and T-cell antigens were not increased (1,6). However, the mechanism of interferon-induced increased expression of surface major histocompatibility antigens is not well understood. We report here the results of a study of the mechanism of increased expression of HLA in a malignant nonlymphoid cell system by analysis of the synthesis of these antigens after interferon treatment. Fur Cells. Four human melanoma cell lines (Hs294T, Hs659T, clone 6, and a clone 6 revertant) were used. The origins and characteristics of these cells have been described (8). Briefly, the Hs294T cell line is sensitive to the antiviral and antigrowth actions of interferon. The clone 6 cells have been isolated from Hs294T, are resistant to both actions of interferon, and are normally maintained in 104 units/ml of interferon. The revertant cell line, obtained by subculturing clone 6 cells in the absence of interferon for 8 wk, is sensitive to the antiviral effect but responds poorly to the antigrowth effect. Hs695T, from the early passages (Hs695-E), is sensitive to the antiviral effect but responds poorly to the antigrowth effect. This cell line became highly sensitive to this latter effect after -60 passages (Hs695-L). The cells were cultured in Dulbecco's modified Eagle's medium (GIBCO)/10% fetal calfserum. Human fibroblast cells were obtained by trypsinization of foreskin and cultivated in minimal essential medium/10% fetal calf serum. In all experiments, th...

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