Anti-erythropoietin receptor (EPO-R) monoclonal antibodies inhibit erythropoietin binding and neutralize bioactivity.
We have generated six high affinity monoclonal antibodies (MoAbs) to the human erythropoietin receptor (hEPO-R) polypeptide. All six MoAbs bind to the extracytoplasmic domain of the hEPO-R, and all immunoprecipitate 35S-labeled hEPO-R from metabolically labeled Ba/F3-hEPO-R cells. Four of the MoAbs neutralize the EPO-dependent growth of Ba/F3-hEPO-R cells, whereas two MoAbs are non-neutralizing. None of the MoAbs inhibit the EPO-dependent growth of Ba/F3 cells expressing the murine EPO-R (mEPO-R), even though the hEPO-R and mEPO-R share 82% amino acid identity. All six of the anti-EPO-R MoAbs bind to the cell surface human EPO-R but none bind to the cell surface murine EPO-R. Of the four neutralizing MoAbs, the one-half maximal inhibition occurs at MoAb concentrations ranging from 1 nmol/L to 50 nmol/L. These MoAbs also compete with radiolabeled EPO for hEPO-R binding. The two non-neutralizing MoAbs fail to inhibit EPO-dependent growth or compete with EPO-binding, even at antibody concentrations as high as 500 nmol/L. The four neutralizing MoAbs, designated group I, compete with each other for an epitope of the hEPO-R polypeptide required for EPO-binding. The two non-neutralizing MoAbs recognize discrete epitopes, and are designated group II and group III MoAbs. In conclusion, this is the first description of MoAbs specific for the hEPO-R. The MoAbs, which recognize three discrete epitopes, may be useful in characterizing the spectrum of cells that display the hEPO-R and in further defining the role of EPO in hematopoiesis.
D'Andrea
A D
AD
Division of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115.
Rup
B J
BJ
Fisher
M J
MJ
Jones
S
S
D000911:Antibodies, Monoclonal / Q000276:immunology*; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions; D000954:Antigens, Surface / Q000276:immunology; D001667:Binding, Competitive; D004306:Dose-Response Relationship, Immunologic; D000939:Epitopes; D004921:Erythropoietin / Q000378:metabolism*; D006801:Humans; D017467:Receptors, Erythropoietin / Q000276:immunology* / Q000378:metabolism
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D000939:Epitopes; D017467:Receptors, Erythropoietin; D004921:Erythropoietin