Biological activity of sera obtained by hyperimmunizing rabbits with interferon from mouse L cells.

Rabbits immunized with interferon from mouse L cells for long periods of time produced interferon-neutralizing antibodies with titers from 1:80 to 1,2000. The anti-interferon sera also contained antibodies against antigens contaminating the interferon preparations such as albumin, bovine gamma-globulin, chicken albumin, extract from L cells, and Sindbis virus antigens. Some sera also displayed cytotoxic activity against cells of transplantable murine leukemia. These antibodies could be removed by specific absorption. Titers of antibodies neutralizing interferon were not correlated with the titers of antibodies against concomitant antigens. In hyperimmunized rabbits interferon-neutralizing antibodies persisted for long periods of time in spite of interrupting immunization.