To detect molecules of Entamoeba histolytica involved in the trophozoite-target cell interaction, three different antisera were generated: (a) two rabbit antisera, one against total amebic proteins and another directed specifically to the 112-kDa adhesin; and (b) a mouse antiserum against amebic molecules adhering to the red blood cell (RBC) surface after incubation of RBCs with total soluble protein from trophozoites (anti-adhesion serum). All three antisera recognized the 112-kDa adhesion. Adhesion of this molecule to the RBC surface was temperature-dependent. More of the 112-kDa adhesion was found on the surface of RBCs incubated with trophozoites at 37 degrees C than on RBCs incubated at room temperature or at 0 degree C. Experiments using both anti-adhesin and anti-total ambebic protein sera revealed the presence of 210, 160, 112, 90, 70, 50, and 24-kDa proteins on RBC incubated with trophozoites. Surface proteins obtained from iodinated MDCK cells recognized amebic proteins of 112, 90, and 48-50 kDa. Virulence-deficient mutants presented a similar amount of the 112-kDa adhesin to the wild-type strain. However, in mutants, the adhesion was not functional, since they did not adhere to RBCs. 90- and 24-kDa proteins were also found to be altered in mutants.