Characterization of Mouse Monoclonal Antibodies to Human Interferon-Gamma

Mouse monoclonal antibodies (mAb) to human interferon-gamma (HuIFN-γ) were characterized. The mAbs studied-E4-18, G4-15, and SAT-1-which are all IgG1-type, reacted to all HuIFN-γ molecular species, both glycosylated and non-glycosylated. Affinity constants calculated of E4-18 and G4-15 didn't have considerable differences for both kinds of HuIFN-γ (1-3×108liter/mol), but SAT-1 had a difference-a higher value (1010liter/mol) for the former than for the latter (8×108liter/mol). In epitope specificity, the results suggested that E4-18 and G4-15 recognized an overlapped region remote from the region of SAT-1. Competition experiment using synthetic peptides suggested that epitope of G4-15 is around N9-26 of the HuIFN-γ sequence. Those mAbs could be used for sandwich radioimmunoassay of HuIFN-γ using double mAbs in two combinations, one (G4-15/E4-18) based on dimer forms of HuIFN-γ and the other (SAT-1/E4-18) based on epitope difference. The mAbs are all neutralizing antibodies in which SAT-1 neutralized at a lower concentration than did G4-15, and at a much lower one than did E4-18. The receptor binding of HuIFN-γ was inhibited by mAbs G4-15 and SAT-1. Efficacy of G4-15 and SAT-1 for the inhibition correspond with that for neutralization.