4. The effect of interferon on the expression of human cell-surface antigens

Abstract

We have studied the effect of highly purified human interferon-α (the NK2-IFN preparation of Secher & Burke (1980)) on the expression of surface antigens by the human cell line Molt 4. Cytofluorimetric analysis with monoclonal antibodies revealed an increase in the membrane expression of HLA-A, B and C but not of other surface antigens. This effect has previously been observed with other human lymphoid cells (Fellous et al. 1979; Heron et al . 1968). The increase in the binding of fluorescent antibody is due to an increase in the number of HLA molecules in the membrane. This was demonstrated in an experiment in which surface proteins were iodinated after treatment with interferon. The difference in the content of HLA molecules could then be visualized on polyacrylamide gel electrophoresis of the immuno-purified surface antigens. In addition, a band corresponding to 16000 M r protein, absent from the surface of several human cell lines, has been found to be induced after IFN treatment. The effect of IFN-α on the synthesis of HLA and β2m was studied by pulse-labelling treated and untreated cells with [ 35 S]methionine for 3 h. The cells were then lysed, and the lysates used for immunoprecipitation with monoclonal antibody for HLA and with rabbit anti-human β2m serum. The immunoprecipitates were then analysed by SDS-polyacrylamide gel electrophoresis. A several-fold increase in the amount of newly synthesized HLA and β2m molecules was clearly observed. These results demonstrate that it is the rate of synthesis of HLA and β2m molecules that has been affected by the interferon treatment, thus leading to the enhanced expression of the antigens on the membrane, and to an increase in the secretion of free β2m.