Transsignaling of soluble receptors of IL-6 family. An IL-6R–expressing cell (left) releases a soluble receptor by shedding or alternative splicing. This soluble receptor binds IL-6 and induces homodimerization of gp130 on a target cell (right) that expresses gp130 but no IL-6R. In this model, the target cell in the absence of soluble IL-6R is not responsive to IL-6. gp130, red; IL-6R black; IL-6, blue. This transsignaling model holds also true for the IL-6 family cytokines IL-11 and CNTF.