Our present knowledge warrants the conclusion that the mechanism causing expulsion of adult T. spiralis is triggered by a specific delayed hypersensitivity reaction. The resultant tissue damage provides the stimuli for initiation of nonspecific allergic inflammation, which in turn directly effects expulsion of worms, probably due to the creation of an unsuitable biochemical environment. Further, the evidence indicates that humoral antibodies at best play only a minor role in the elimination of worms. Nevertheless, they are important in the total immunity in that they produce direct deleterious effects against the worms, such as interference with growth and reduction of the reproductive potential, and they are responsible for contributing to cellular destruction as a consequence of anaphylactic hypersensitivity reactions.
Considerable work remains to clarify various aspects of the delayed response to T. spiralis, such as demonstration of the responsible antigen(s) and, by electron microscopy, the true identity of the immunologically competent cells. In the meantime, it is hoped that the present findings will encourage others to study this phenomenon and its relation to immunity demonstrated against other parasitic agents.
Professor and Head, Department of Parasitology, and Assistant Dean, School of Public Health, University of North Carolina at Chapel Hill, 27514.