A monoclonal antibody to alcohol dehydrogenase cross-reacts with human complement component C3

: A monoclonal antibody (mHADH1) against alcohol dehydrogenase was found to cross-react with an abundant protein in human serum. This cross-reacting material was identified unambiguously as the third component of complement (C3), probably part of the alpha-chain, by immunoblotting and immunoprecipitation experiments. The known ADH epitope, HVLPF, recognized by the monoclonal antibody is not, however, present in the C3 sequence.