Model of IL-11 antagonism by sIL-11R. (A) Cells expressing excess gp130-sIL-11R will bind IL-11 and complex with free gp130, thus augmenting the IL-11 response. (B) Cells with limiting gp130 in the presence of limiting IL-11 addition of sIL-11R will compete with the transmembrane IL-11R for IL-11, and antagonism will occur provided K₂ <K₃ . K₁ = affinity of ligand for IL-11R (soluble or transmembrane). K₂ = affinity of IL-11/sIL-11R complex for membrane-bound gp130. K₃ = affinity of IL-11/transmembrane IL-11R complex for membrane-bound gp130. The + refers to the intensity of the signal generated.