N-Acetyl-D-galactosamine-inhibitable adherence lectin of Entamoeba histolytica. II. Mitogenic activity for human lymphocytes.

A soluble protein preparation from virulent axenic amoebae (strain HM1-IMSS) has been demonstrated to be mitogenic for normal human lymphocytes; mitogenesis was optimal at 100 micrograms/ml when incubation was maintained for five to seven days with monocytes (P less than .001). After gel filtration chromatography mitogenic activity of fractions was associated with N-acetyl-D-galactosamine-inhibitable lectin activity (agglutination of Chinese hamster ovary cells; P less than .001). Lymphocyte proliferation induced by these active fractions was specifically inhibited by asialofetuin (P less than .001), which contains three terminal beta 1-4 linked galactose residues. In four strains of axenic amoebae mitogenic activity of soluble protein preparations correlated with in vitro virulence and lectin activity for Chinese hamster ovary cells. The amoebic N-acetyl-D-galactosamine-inhibitable lectin appears to be responsible for the mitogenic activity of soluble amoebic protein preparations; alteration of cell-mediated immunity by this amoebic moiety could potentiate in vivo virulence of the parasite.