Unusual precipitins in pathological human sera.

In conducting double diffusion gel precipitation tests, unexpected, strong precipitation reactions were noticed between a serum originating from a renal graft recipient and many pathological human sera. The highest frequency of positive reactions were produced by sera of patients with infectious mononucleosis (83%), chronic Epstein-Barr virus infections (72%), rheumatoid arthritis (57%), lepromatous leprosy (57%), and AIDS (44%). The precipitin in these pathological sera was identified as an antibody of IgM variety and the precipitinogen in the transplantation serum was shown to be a thermostable component with beta-globulin mobility. No explanation of the nature of reactions observed can be given at present.