Oncostatin M (OSM), a member of the IL-6 family of cytokines, interacts with low-affinity receptor subunit monomers and high-affinity heterodimeric receptor complexes composed of members of the class I cytokine receptor family. Important species-specific differences in receptor binding have been identified. OSM binds directly with low-affinity to gpl30, which was originally characterized as the signal transducer sub-unit within the high-affinity IL-6 receptor complex.