A monoclonal anti-human IL-6 receptor antibody inhibits the proliferation of human myeloma cells

A monoclonal antibody (UV4) against the human IL-6 receptor (hIL-6R) was generated by immunizing BALB/c mice with both a human myeloma cell line (U266) and a murine cell line (M12.4/R) transfected with the hIL-6R cDNA. Flow cytometric analysis demonstrated that UV 4 stains the hIL-6R⁺ cell lines U266 and U937, but not the hIL-6R^- cell lines Daudi and K562. Competitive inhibition assays demonstrated that preincubation of U266 cells with UV4 inhibited the binding of a phycoerythrin (PE)-IL-6 conjugate to the hIL-6R and also inhibited the proliferative activity of IL-6 on the IL-6- dependent human myeloma cell lines ILKM2 and ILKM3. In contrast, UV4 did not interfere with the proliferation of the hIL-6R^- Burkitt's lymphoma cell line, Daudi. Direct sandwich radioimmunoassays further confirmed that the UV4 bound to the same molecule as the goat anti-hIL-6R antibody. These results suggest that both UV4 and human IL-6 bind to the same or adjacent epitopes on the hIL-6R. This monoclonal antibody should facilitate studies of the structure-function relationship of IL-6R and may be useful for the treatment of IL-6-dependent diseases such as multiple myeloma.