Abstract
The crude extract derived from seeds of Artocarpus integrifolia (jack fruit) contains two fractions with different biological activities for lymphocytes. One fraction is the d-galactose-binding lectin, jacalin, obtained by affinity purification on a d-galactose agarose column. The other, which is a component of the flow-through fraction (FT), is responsible for the mitogenic activity observed with human PBMC and murine spleen cells. In contrast, jacalin inhibits FT- and ConA-induced proliferative activity of human PMBC and murine spleen cells. This inhibition is not due to toxicity, because: (1) jacalin induces significant levels of IL-3/GM-CSF but not of IL-2 and/or IL-4 in murine spleen cells; (2) jacalin does not affect the capacity of these cells to secrete IL-2 or IL-4 as supernatants obtained from spleen cells sequentially stimulated with jacalin and ConA contain IL-2 and/or IL-4 as well as IL-3/GM-CSF. The ligand for the mitogen contained in the FT fraction is d-mannose as determined by sugar inhibition studies.