Characteristics of the Hemagglutinin Produced During Plasmodium lophurae Malaria in Chickens.

During the course of Plasmodium lophurae infections in normal chickens, there was a sharp increase in the titer of a hemagglutinin which reacted better with trypsinized than with normal erythrocytes. This hemagglutinin was a typical "cold hemagglutinin" in that it was much more active at 4 C than at 37 C, was found in the macroglobulin fraction of the serum, was eluted from erythrocytes at 37 C, and was easily destroyed by 2-mercaptoethanol reduction. The injection of allogeneic erythrocytes into chickens prior to their exposure to P. lophurae resulted in a coexistent increase in cold hemagglutinin titers and enhanced resistance to parasitemia. Since this antibody was more active against altered erythrocytes than against normal erythrocytes, it may moderate resistance to malarial infections by specifically stimulating phagocytosis of parasitized erythrocytes.