Hematopoietic tissue allografts in Biomphalaria glabrata (Mollusca : Pulmonata) induce humoral immunity to Schistosoma mansoni

We examined a potential mechanism for adoptively transferred resistance aga inst Schistosoma mansoni in schistosome-susceptible snails receiving allogr afts of the hematopoietic amebocyte-producing organ (APO) from a schistosom e-resistant strain of Biomphalaria glabrata. Susceptible NIH albino snails first were implanted with the APO from resistant Salvador strain donors. At 14 days post-implantation, cell-free plasma was isolated front APO recipie nts and injected into a second group of NIH albino snails. Controls were in jected with plasma from NIH albino snails that previously had received impl ants of Salvador mantle, an immunologically inert tissue. Finally, plasma r ecipients, along with untampered (non-injected) controls, were exposed to m iracidia of S. mansoni and subsequently monitored for infection. A signific antly lower prevalence of infection occurred in the group injected with pla sma from APO recipients (53%) in comparison with that in untampered control s (100%) or in snails receiving plasma from mantle recipients (97%). These results suggest that adoptively transferred resistance in B. glabrata resul ts from secretion of soluble resistance factor(s) by the implant, rather th an, or in addition to, formation of a hemocyte chimera having cytotoxic don or hemocytes. (C) 2001 Elsevier Science Ltd. All rights reserved.