[Immunobiology of snails infected with developmental stages of digenetic trematodes]

Susceptibility of snails to infection with larvae of digenetic trematodes is determined by: degree of infectivity of a parasite race, causal ecological factors, and efficiency of defence reactions. In the article indications of resistance and immunity of these animals to such infections are presented, with regard to mechanisms of cellular and humoral forms of the immunological response. Some aspects of altered by a parasite dynamics of defence reactions of a host, like: occurrence of opportunistic infections (development of the immunological tolerance state for homo- and heterologous reinfections), adaptive immunity, and cases of survival of parasitic larvae in naturally resistant snails are discussed.