Functions as an intestinal M-cell transcytotic receptor specific of type-I-piliated bacteria that participates in the mucosal immune response toward these bacteria. At the apical membrane of M-cells it binds fimH, a protein of the bacteria type I pilus tip. Internalizes bound bacteria, like E.coli and S.typhimurium, from the lumen of the intestine and delivers them, through M-cells, to the underlying organized lymphoid follicles where they are captured by antigen-presenting dendritic cells to elicit a mucosal immune response. Interacts with SYCN. Secreted, after cleavage, in the pancreatic juice. Specifically expressed by M (microfold) cells which are atypical epithelial cells of the intestine. N-glycosylated. Knockout mice lacking Gp2 fail to induce antigen-specific helper-T-cells and antibody immune responses after oral immunization with FimH positive bacteria (PubMed:19907495). This is not due to a general defect in the immunological functions, since a normal response is induced by other systemic immunizations (PubMed:19907495).