Fig. 3

The upper panel of this figure illustrates the partial immune responses triggered by pathogen invasion in Biomphalaria glabrata. Several immune-related factors and their mechanisms of action have been reported in smooth-bore snails. BgTLR, as a crucial transmembrane PRR, mediates immune signaling in haemocytes through intracellular transduction. Soluble immune factors like BgFREP, BgTEP, and Biomphalysin interact to initiate cytotoxic effects (perforation of pathogen cell membranes or release of cytotoxic substances) and opsonization, culminating in pathogen elimination via cell phagocytosis. Additionally, the chemoattractant factor BgMIF induces haemocyte migration and proliferation, potentially contributing to encapsulation response. In contrast, the lower panel describes the immune response following pathogen invasion in Oncomelania hupensis. Research in this area remains relatively scarce. To date, only directly related immune factors, OhTLRs and OhMIF, have been identified and functionally characterized, with other immune-related factors and their associated mechanisms largely unknown