Heat-labile IgG2a antibodies affect cure of Trypanosoma musculi infection in C57BL/6 mice.

Immune plasma (IP) obtained from mice cured of Trypanosoma musculi infection is able to mediate trypanosome clearance both in vivo and in vitro. A protein A-derived immunoglobulin fraction of IP containing primarily IgG2a and IgG3 shares this curative activity. Additional purification of IP with the use of anti-IgG2a and anti-IgG3 coupled to Sepharose beads demonstrates that the curative activity of IP resides solely in the IgG2a fraction; IP depleted of IgG2a is no longer able to effect T. musculi removal. Furthermore, this curative IgG2a is labile to heat treatment for 30 min at 56 degrees C. Enzyme-linked immunosorbent assays show that trypanosome-specific IgG2a builds up gradually over the course of infection, and temporarily drops slightly at the time of parasite clearance.