Monoclonal antibodies against the human interleukin-11 receptor alpha-chain (IL-11Rα) and their use in studies of human mononuclear cells

A panel of 14 hybridoma cell lines secreting monoclonal antibodies against the human interleukin-11 receptor alpha chain (hIL-11Rα) was obtained using two different approaches. Two antibodies were raised against peptides of the N- and C-terminal sequences, respectively, of the extracellular part of the hIL-11Rα. Another group of 12 antibodies was generated against a hybrid protein consisting of the extracellular part of the hIL-11Rα fused to mature full-length human IL-2. All these antibodies recognized native hIL-11Rα and most also recognized the denatured receptor on immunoblots after SDS–PAGE. Four different epitopes were identified on the extracellular part of the hIL-11Rα. One epitope, defined by the E27 antibody, is located at the N-terminus and the other three epitopes are clustered in the membrane-proximal, C-terminal region. The antibodies defining epitopes I and II recognized membrane-bound hIL-11Rα expressed in gp130/hIL-11Rα-co-transfected Ba/F3 cells. The E27 antibody cross-reacted with murine IL-11Rα, in agreement with the fact that the N-terminal region is highly conserved between species. The other 13 antibodies all recognized a region between amino acids 319 and 363, which is the membrane-proximal part of the hIL-11Rα. This region, which is less conserved between mouse and human, is shown here to be an immunodominant region. Anti-IL-11Rα monoclonal antibodies, which have not been described previously enabled us to explore the expression and tissue distribution of IL-11Rα on human peripheral blood mononuclear cells and cell lines. The antibodies provide powerful tools for the study of the regulation and function of the receptor.