Development of horse polyclonal antiserum inhibiting all in vitro biological functions of human IFN-gamma

Following a standard immunization protocol with recombinant human interfero n-gamma (IFN-gamma), a horse polyclonal antiserum was obtained and evaluate d for its ability to interfere with multiple IFN-gamma activities in vitro. Data obtained show that polyclonal horse antiserum neutralizes the antipro liferative activity of IFN-gamma, inhibits the binding of IFN-gamma to cell ular receptors, and can up-regulate HLA-DR antigen expression and interfere with its antiviral activity. The broad neutralizing capacity of horse poly clonal antiserum has been assessed on cell lines which differ as to origin and sensitivity to IFN-gamma. Moreover; we observed that this antiserum cou ld inhibit the binding of radiolabeled IFN-gamma to its cellular receptor, its subsequent internalization into the target cell, and its antiviral acti vity. As it is able to inhibit all the biological activities of IFN-gamma, this antiserum might provide new therapeutic approaches to diseases with ev idence of activated cell-mediated immunity.