CTB binds to Le^X linked to proteins but not ceramide.

(A) GM1- or Le^X-os (oligosaccharide) linked to ceramide and immobilized to wells were detected with ¹²⁵I labeled CTB. Relative binding is displayed as counts per minute (CPM). (B-C) ELISA with titrated amounts of os-linked to HSA, immobilized to wells and detected with (B) CTB-HRP and (C) G33D-HRP. Graph shows absorbance values from three independent experiments. (D) ELISA with os-linked to HSA, immobilized in wells and then blocked with indicated concentrations of anti-Le^X antibody HI98 or isotype control (IgM), and detected with CTB-HRP. Graph shows absorbance values from one representative out of two independent experiments. (E) ELISA with os-linked to HSA, immobilized in wells and detected with CTB-HRP in the presence of increasing blocking concentrations of tri-Le^X-os and GM1-os. Graphs show absorbance values from one representative out of two independent experiments.