Dl. Cooke et Sp. Borriello, NONSPECIFIC-BINDING OF CLOSTRIDIUM-DIFFICILE TOXIN-A TO MURINE IMMUNOGLOBULINS OCCURS VIA THE FAB COMPONENT, Infection and immunity, 66(5), 1998, pp. 1981-1984
Clostridium difficile toxin A binds nonspecifically to a mouse monoclo
nal antibody (MAb) immunoglobulin G3 lambda chain [IgG3(lambda)], thro
ugh the Fab component. This binding, which is retained even after boil
ing the MAb, is temperature dependent, with more toxin bound at 4 than
37 degrees C (P = 0.0024), The nonspecific binding was decreased by i
ncubation of the IgG3 lambda MAb with alpha- or beta-galactosidase (P
= 0.0001 and 0.029, respectively), indicating that toxin A binds to a
carbohydrate moiety on the Fab, However, binding was not blocked by th
e Bandeiraea simplicifolia lectin BS-1, indicating that a terminal alp
ha-galactose may not be involved, Binding was also not affected by com
petitive assays with Lewis X antigen. The dependence on carbohydrate m
oieties in nonspecific binding was also shown for two other MAbs, IgA(
kappa) and IgM(lambda), with demonstration of a significant reduction
in binding,vith a-galactosidase (P = 0.0001 and 0.0002, respectively)
but not beta-galactosidase (P = 0.27 and 0.25, respectively).