SYNERGISTIC MONOCLONAL-ANTIBODIES INTERACTIONS AND THEIR USE FOR DETERMINATION OF ANTIBODY SPECIFICITIES

Three monoclonal antibodies (MAb 3C11, F11 and 10D6) to human growth h ormone (hGH) recognize independent epitopes and show mutually enhancin g properties. Thus, I-125-hGH binding to each of these MAb augmented s ignificantly in the presence of each one of the other two MAb. Moreove r, preincubation of the hormone with paired MAb gave rise to ternary c omplexes (Ag: Ab1: Ab2) which bound better than the free tracer to the third MAb previously captured on a solid-phase. Highly stable quatern ary complexes (Ag: Ab1: Ab2: Ab3) were thus formed. Since Fab fragment s from the three MAb displayed the same behavior as the whole Ab molec ule, neither the formation of multimolecular cyclic complexes nor the occurrence of interactions through Fc fragments could explain the reci procal MAb binding enhancement. Therefore, the results obtained sugges t that MAb 3C11, F11 and 10D6 produce some modification in the Ag, eac h one improving the binding of the two other MAb. Additionally, the in hibition of the formation of quaternary complexes between the MAb and hGH was used to evaluate specific Ab populations in polyclonal antiser a, avoiding the masking effect of enhancing Ab. The results obtained i ndicate that Ab directed to the hGH antigenic domains defined by MAb 3 C11, F11 and 10D6 could be detected in spite of the presence of enhanc ing Ab to all three MAb.