Over the last ten years there has been a steadily increasing effort in the field of schistosome immunology, and the greater part of this activity has had the long term aim of producing an effective anti-schistosome vaccine. It seems likely that the development of such a vaccine will depend on an improved understanding of the biology of the schistosome surface. Available evidence suggests that surface antigens of the young parasite act as targets for the host's immune attack. These target antigens apparently become hidden from the host as the parasite develops; in this way host immunity is evaded.
In this paper we review the current information on the nature of the schistosomular surface and the changes which take place there as a result of host-parasite interaction.
Unlike the nematode, the schistosome is not bounded by a chitinous-like cuticle but by a syncytial layer of cytoplasm bounded by a living plasma membrane (Fig. 1) which has important physiological and absorptive functions.