Plays a key role in innate immunity by acting as a pattern recognition receptor for beta-1,3-glucan from fungi and lipopolysaccharide from Gram-negative bacteria (PubMed:10827089). Upon recognition of invading microorganism-derived products, acts upstream of protease spz processing enzyme SPE to activate the Toll pathway and to induce the expression of antimicrobial peptides drosomycin, cecropin and attacin (PubMed:10827089, PubMed:16399077). Secreted and attached to the membrane by a GPI-anchor. Expressed at moderate levels throughout the life cycle. Belongs to the insect beta-1,3-glucan binding protein family.