CONTACT-DEPENDENT TRANSFER OF THE GALACTOSE-SPECIFIC LECTIN OF ENTAMOEBA-HISTOLYTICA TO THE LATERAL SURFACE OF ENTEROCYTES IN CULTURE

In a study to investigate early interactions of Entamoeba histolytica with epithelial cell monolayers, we found that a monoclonal antibody ( MAB), CD6, against an ameba surface antigen recognized the lateral sur face of epithelial cells after coculture with trophozoites. Display of the CD6 antigen on the epithelial cells necessitated contact with act ive trophozoites. It was found neither at 4 degrees C, nor with prefix ed trophozoites, nor with trophozoite-conditioned media, nor when a fi lter prevented direct contact, Monolayers exposed to amebic sonicates or detergent lysates showed random immunostaining, Access to the antig enic site was Limited, as immunostaining occurred predominantly with s ubconfluent monolayers, CD6 epithelial cell binding was first observed after 5 min of coculture; trophozoite-mediated target cell lysis was not detected until 15 min following coculture, Epithelial cell immunos taining occurred with some other ameba-specific antibodies but not wit h MAbs raised against the 170-kDa subunit of the galactose-N-acetylgal actosamine (Gal/GalNAc)-specific lectin, The CD6 MAb as well as some o ther ameba-specific antibodies immunoprecipitated from trophozoite lys ates the same bands as the MAbs against the cysteine-rich domain of th e 170-kDa subunit of the Gal/GalNAc-specific lectin, Why the latter MA bs failed to stain epithelial cells in the vicinity of attached tropho zoites is presently unknown. We concluded that E. histolytica trophozo ites transferred the intact amebic Gal/GalNAcspecific lectin or a port ion of it to the lateral surface of epithelial cells, This juxtacrine transfer preceded killing of target cells.