Production of intestine-specific monoclonal antibody and interspecific cross-reaction in triclads and polyclads

We have produced a monoclonal antibody (mAb(2)2B6) specific to intestinal and epidermal cells of Dugesia japonica. This mAb(2)2B6 also reacted with the secretory granules of a kind of sub-epidermal gland cells, epithelial cells and gland cells in the pharynx. The results of the interspecific cross-reaction tests with four other freshwater triclads and four polyclads showed that this mAb(2)2B6 can be used as a marker, specific to only intestinal cells in both Planocera multitentaculata and Planocera reticulata of polyclads. Immuno-electron microscopical research revealed that the cytoplasm of phagocytic cells and the spherical large granules in granular clubs reacted strongly to this mAb in the intestine. Also, mAb positive material seemed to be absorbed by pinocytosis from phagocytic cells into the granular clubs. These observations support the theory that the granular clubs are protein reserve cells, not gland cells for intraluminal digestion.