Cardiotrophin-1 (CT-1) is a member of the cytokine family which also includes IL-6, IL-11, l LIF, CNTF, OSM. CT-1 has since been shown to be a pleiotrophic cytokine with overlapping actions with other IL-6 family members on a variety of cell types. Biologically active human CT-1 is synthesized as a 201 amino acid polypeptide lacking a hydrophobic N-terminal secretion signal sequence. Recombinant Human CT-1 is a 21.1 kDa protein consisting of 200 amino acid residues.