Ja. Smith et al., CLOSTRIDIUM-DIFFICILE TOXIN-A BINDING TO HUMAN INTESTINAL EPITHELIAL-CELLS, Journal of Medical Microbiology, 46(11), 1997, pp. 953-958
Clostridium difficile radiolabelled toxin A ([H-3]-toxin A) bound to h
uman duodenal and colonic epithelial cells isolated from endoscopic bi
opsies, Binding was greater at 4 degrees C than 37 degrees C, consiste
nt with the thermal binding characteristic of toxin A to a carbohydrat
e moiety, At 37 degrees C colonic cells bound significantly more [H-3]
-toxin A than duodenal cells, The amount of [H-3]-toxin A binding vari
ed considerably between individuals, [H-3]-toxin A was displaced by un
labelled toxin A by 50% for duodenal cells and 70% for colonic cells w
ith 94.3 nM unlabelled toxin A, Low non-displacable binding was observ
ed in some samples at 4 degrees C and 37 degrees C, suggesting that th
ese cells came from individuals incapable of specifically binding toxi
n, Pre-treating cells with alpha- or beta-galactosidases to cleave ter
minal alpha- and beta-galactose residues reduced [H-3]-toxin A binding
, There was also a reduction in [H-3]-toxin A binding after heat treat
ing cells, which is suggestive of protein binding, The reduction in bi
nding varied between individuals, The reduction of [H-3]-toxin A bindi
ng, after the removal of beta-linked galactose units, implicates these
as components of the receptor and adds credence to the idea that the
Lewis X, Y and I antigens may be involved in toxin A binding to human
intestinal epithelial cells, However, because the Lewis antigens do no
t possess terminal alpha-galactose units, the reduction in binding aft
er alpha-galactosidase treatment suggests that other receptors may be
involved in toxin A binding to some human intestinal cells, These data
are the first demonstration of direct toxin A binding to human intest
inal epithelial cells.