Kinetics of Immunological Responses, Resistance to Reinfection, and Pathological Reactions to Infection with Trichinella spiralis

Changes in immune responses, resistance to reinfection, and pathological reactions were studied serially in mice that had been infected for four to 40 weeks with 150 larvae of Trichinella spiralis. Immediate footpad hypersensitivity reactions to anti-gens of Trichinella were present throughout the period of observation. Delayed hy-persensitivity reactions 48 hr after injection of antigen were first seen in mice infected for 14 weeks and gradually increased in size thereafter. Intestinal adult worm bur-dens were determined one week after challenge with 500 larvae. There was resistance to reinfection and accelerated expulsion of worms in animals challenged three weeks after the primary infection; this resistance waned at seven and 13 weeks but reap-peared in mice infected for 20 weeks or longer. Counts of larvae in muscle were deter-mined four weeks after challenge with 500 larvae. Marked resistance was present four weeks after the primary infection and was maintained for the duration of the study. Most investigations of the immunology of trichi-nosis have been concerned only with the early stages of infection with Trichinella spiralis. Al