Binding of class II Escherichia coli enterotoxins to mouse Y1 and intestinal cells

The binding of class II Escherichia coli heat-labile enterotoxins (LT) to Y1 tissue-cultured cells and mouse intestinal cells was studied and compared with that of class I toxins, including cholera enterotoxin. All radioiodinated (125I) toxins retained their biological activities in both model systems, but only LTIIb could be shown to bind specifically to target cells. LTIIa could inhibit the binding of both class I and LTIIb toxins, a finding which correlates with its ability to bind to multiple gangliosides. LTIIb could not inhibit the binding of the other enterotoxins. The binding and activity of class II toxins could not be modulated by prior exposure of target cells to the B subunit of LTI.