Some biological activites of rabbit anti-interferon serum.

After prolonged immunization of rabbits with a semipurified mouse interferon preparation in Freund-incomplete and/or Al-Span-Oil-adjuvant a specific interferon neutralizing immunoglobulin was obtained from antiserum. The specific activity of the antiserum and immunoglobulin was confirmed in tests in which the interaction of antibodies with the cell-surface was ruled out. The antiserum (and the immunoglobulin) neutralized both the anti-viral and the cell-growth inhibitory activity of interferon. The "slow" and the "fast" fractions of purified interferon preparations were equally sensitive toward the neutralizing effect of antibodies. On the other side, the reaction of heat-inactivated interferon with the antiserum did not diminish its neutralizing activity suggesting a destruction of interferon-antigenic sites.