Characterization of antibodies mediating protection and cure of Trypanosoma musculi infection in mice.

Plasma samples were collected from mice infected with Trypanosoma musculi at different times postinfection and administered to naive recipient mice either before or during T. musculi infection. The protective and curative activities of these plasma samples were shown to increase as the time of collection postinfection increased; plasma collected at 14 days postinfection was partially protective and partially curative, whereas that collected at 28 days postinfection was completely protective and curative. The curative activity was labile to heat treatment (30 min at 56 degrees C), whereas the protective activity was heat stable. Additional kinetic parameters relating to the efficacy of protection were investigated. Evidence is presented that both activities are immunoglobulin in nature. Protein A-Sepharose chromatography indicated that the activities are associated with the immunoglobulin G2a or immunoglobulin G3 subclasses of immunoglobulin G. The curative antibody appears to be intrinsically heat labile, since heat treatment of a purified immunoglobulin preparation abolished the ability to cure. Studies on the mechanism of parasite elimination from blood suggest that the process not only requires antibody but is also complement dependent.