Immunology of schistosomiasis

This Memorandum, after summarizing the life cycle of the different species of human schistosome, reviews the present knowledge of the immunology of schistosomiasis. Each stage of the parasite contains antigen that may stimulate an immune response. However, at the moment there are no accepted serological in vitro tests that correlate with protection; this develops only after the host has experienced a living infection, which suggests that the stimulation of immunity is due to some metabolic process involving the release of protective antigen. The adult worm, however, seems to be able to escape the immune mechanism of the host. Specific antigens are also released by the eggs, and the immune response against these antigens seems to cause granuloma formation around the egg itself. The granuloma is the main lesion found in schistosomiasis. Evidence for protective immunity in experimental animals and man is reviewed, together with the possible mechanism by which the adult worm escapes the immune response of the host. A review of methods used for the diagnosis of schistosomiasis and a list of recommendations for further research are also included.