Biological activity of sIL-11R on M1 cells.(A) sIL-11R titration in the presence of saline (□) or 500 pmol/L IL-11 (▪). (B) IL-11 titration in the presence of 40 nmol/L sIL-11R (□) compared with cells expressing the transmembrane IL-11R (▪) in the absence of sIL-11R. Dose response measured by the ability to induce differentiation in M1 cells and thereby reduce ³H-thymidine incorporation. Results expressed as mean and standard deviation of triplicate wells from 2 representative experiments.