Anti-immunoglobulins and heterophil agglutinins in experimental trypanosomiasis.

Rheumatoid factor (RF)-like substances and heterophil agglutinins (HA) were induced in rabbits by infection with a strain of Trypanosoma equiperdum. Infection with a T. gambiense strain produced HA, but no RF. RFs appeared usually before immunoglobulin G (IgG) levels started to increase. They disappeared spontaneously after 4 to 6 weeks. HA were of the IgM class, appeared within 1 to 2 weeks after infection, and usually remained at high levels afterwards. They could not be absorbed out with lyophilized whole trypanosomes. Therapy suppressed the formation of RF as well as of HA, but IgG complexes as well as antibodies against trypanosomal antigens remained present for considerable periods after the installment of therapy. It is concluded that RFs are not induced by IgG complexes. The results suggest that HA are probably not cross-reacting antibodies induced by trypanosomal antigens.