An anti-digoxin monoclonal antibody seems to express more than one functional paratope

An anti-digoxin monoclonal antibody (mAb 4G3) has been produced and characterized with respect to its fine specificity and affinity. In an independent series of experiments anti-idiotypic monoclonal antibody (mAb 7G9) was selected which reacted with the antigen-binding center of an anti-human chorionic gonadotropin monoclonal antibody (anti-hCG mAb 1B10). In detailed studies on its binding characteristics it has been shown that mAb 4G3 binds to an anti-idiotypic monoclonal antibody mAb 7G9 in solution. Western blotting experiments showed that mAb 4G3 reacted against antiidiotypic antibody under non-reducing conditions, only. Moreover, mAb 4G3 has been shown to express self-binding properties. Absorption with saturating amounts of its specific hapten, i.e. digoxin, did not change the binding of mAb 4G3 to anti-idiotypic antibody and its self-binding ability. It is speculated on the basis of these data that mAb 4G3 possesses more than one functional paratope.