A monoclonal antibody against the ligand binding site of the receptor for mouse interferon-gamma.
A rat monoclonal IgG2a antibody, GR-20, has been produced against the receptor for mouse interferon-gamma (MuIFN-gamma). Comparison of competitive binding studies performed with either 125I-labeled GR-20 or recombinant (r) MuIFN-gamma, as well as a variety of other studies, suggested that the epitope recognized by the monoclonal antibody (mAb) is in the domain of the receptor that binds ligand. The binding of GR-20 to cells of the monomyelocytic line WEHI-3 was of high affinity (1-2 nM). Approximately 20,000 binding sites were found per cell, a value that is in close agreement with the number of MuIFN-gamma receptors quantified on cells of the same type by ligand binding studies. The mAb also bound to a variety of other mouse cells, suggesting that the same epitope is shared by receptors for MuIFN-gamma, regardless of cell type. The epitope was not detected on two human cell types that were tested, while cells of a rat cell line shown to be minimally responsive to rMuIFN-gamma gave equivocal binding results when they were interacted with GR-20. Binding of the mAb to the receptor did not mimic the effects of ligand. In fact, the opposite was true: binding blocked the induction of three biological effects of MuIFN-gamma, including priming of macrophages for tumor cell killing, upregulation of the expression of class II major histocompatibility antigens (Ia) on the same cell type, and induction of antiviral activity in L cells. Following intravenous injection, initial removal of GR-20 was precipitous, followed after 1 h by a phase which was more gradual, resulting in 5-10% of biologically active mAb remaining in the circulation after 24 h. Such retention should make this mAb useful in a variety of studies in vivo.
Basu
M
M
Wilkinson Laboratory for Cancer Research, University of Kansas Cancer Center, Kansas City.
Pace
J L
JL
Pinson
D M
DM
Russell
S W
SW
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D001665:Binding Sites; D002478:Cells, Cultured; D000939:Epitopes / Q000276:immunology*; D006801:Humans; D051379:Mice; D051381:Rats; D011971:Receptors, Immunologic / Q000276:immunology*; D017471:Receptors, Interferon
D000911:Antibodies, Monoclonal; D000939:Epitopes; D011971:Receptors, Immunologic; D017471:Receptors, Interferon