Isolation and characterization of monoclonal antibodies directed to rat interferon-gamma.

Eight stable hybridoma cell lines producing monoclonal antibodies reactive with rat interferon-gamma have been generated. The antibodies produced belong to three different immunoglobulin isotypes: IgG1 (4 monoclonal antibodies, designated DB-1, DB-10, DB-12 and DB-13), IgG2a (3 monoclonal antibodies, DB-9, DB-14 and DB-16) and IgA (1 monoclonal antibody, DB-2). The antibodies were characterized in terms of epitope specificity and reactivity with rat, mouse and human interferon-gamma. Three antibodies (DB-1, -2 and -14) show high antiviral neutralizing activity against natural and recombinant DNA derived rat interferon-gamma, whereas the others have low (DB-10, -12, -13 and -16) or no (DB-9) detectable activity. Two antibodies (DB-1 and -2) effectively bind and neutralize mouse interferon-gamma, one antibody (DB-14) exhibits some cross-reactivity and the others show no reactivity towards the mouse lymphokine. None of the antibodies reacts with human interferon-gamma. All antibodies recognize immunoblotted recombinant rat interferon-gamma, although substantial variation in the immunoreactivity existed. Competition binding experiments reveal that the antibodies are directed to three spatially distinct sites on the rat lymphokine. Two non-competing monoclonal antibodies were selected and used for the development of a specific enzyme-linked immunosorbent assay for the detection of rat interferon-gamma in biological fluids.