Local anaphylactic reactions to the penetration of cercariae of Schistosoma mansoni.

1. In order to study local tissue anaphylactic responses to infection with Schistosoma mansoni cercariae, mice of three different strains (C57BL/10J, Balb/cJ and CBA/J) were infected by subcutaneous injection of 15 to 20 cercariae. Eleven to 16 weeks later the animals were reinfected through one ear with 250 to 350 cercariae. 2. Throughout the infection period, the histamine content of the ears increased up to 150% of control values. Upon reinfection, the penetration of cercariae through the ear reduced its histamine content to near normal values. 3. Reinfection causes inflammation as judged by a 1.5 to 2.3-fold increase in the amounts of plasma leaking through the ear vessels as measured by leakage of Evans blue dye. 4. These results suggest that the local inflammatory reaction mediated by mast cells is important in the resistance of mice to reinfection with S. mansoni.