Distinct functional domains on the recombinant human immune interferon molecule

Two monoclonal antibodies directed against distinct epitopes of recombinant human immune interferon (rIFN-gamma) were used to investigate the relationship between the molecular organization of IFN-gamma and its various biological activities on cultured human melanoma cells. Both monoclonal antibodies inhibited the increase in the expression of cell surface human lymphocyte antigens Class I and II antigens and the antiproliferative and antiviral actions of rIFN-gamma. On the other hand neither monoclonal antibody affected the binding of rIFN-gamma to melanoma cells and its ability to reduce the expression of a high molecular weight-melanoma associated antigen. These data indicate that the functional domains of IFN-gamma responsible for antiviral activity, increased human lymphocyte antigen expression and antiproliferative effects on human melanoma cells may be distinct from that (those) involved in reduced expression of the high molecular weight-melanoma associated antigen and in IFN-gamma binding to cell receptors.