SERUM-INDEPENDENT AND SERUM-DEPENDENT CYTOADHERENCE IN THE INTERACTION OF ENTAMOEBA-HISTOLYTICA WITH MAMMALIAN TARGET-CELLS

Entamoeba histolytica kills target cells only on direct contact, sugge sting that trophozoite-mediated cytolysis is initiated by the contact between trophozoites and target cells. We have shown that adherence be tween E. histolytica and target cells (polymorphonuclear granulocytes, erythrocytes, Chinese hamster ovary cells, human colon carcinoma cell s) was inhibited by specific carbohydrates, and adherence between E. h istolytica and polymorphonuclear granulocytes (PMN) was enhanced by pr eincubation of the trophozoites with serum. Inhibition of adherence cl early paralleled inhibition of cytolysis and phagocytosis of target ce lls. Cytolysis of PMN, however, was not increased by preincubation of the trophozoites with serum. These results suggest that the effector f unctions of trophozoites are only dependent on carbohydrate-specific a dherence mechanisms mediated by the amoebic Gal/GalNAc-binding lectin. E. hisiolytica trophozoites themselves can be killed by PMN, dependin g on the virulence of the trophozoites. PMN could not kill E. histolyt ica trophozoites more effectively when the adherence was enhanced by p reincubation of the trophozoites with serum or when adherence was only mediated by serum-dependent mechanisms.