Summary

In this review, the phenomenon of delayed hypersensitivity is characterized briefly, and, based on recent reports, its apparent demonstration in immunity to Trichinella spiralis, Trichostrongylus colubriformis, Ancylostoma caninum, Fasciola hepatica, and Hymenolepis nana is presented. The prominent role of this phenomenon in the mechanism of immunity to adult T. spiralis is explained, and then consideration is given separately to each of the other parasites to offer by speculation an explanation for the reported results.