In complex with CRLF1, forms a heterodimeric neurotropic cytokine that plays a crucial role during neuronal development (By similarity). Also stimulates B-cells. Binds to and activates the ILST/gp130 receptor (PubMed:10500198). Forms a heteromeric complex with cardiotrophin-like cytokine CRLF1/CLF-1; the CRLF1-CLCF1 complex is a ligand for the ciliary neurotrophic factor receptor/CNTFR. The CRLF1-CLCF1 heterodimer binds SORL1 (via N-terminal ectodomain); within this complex, the interaction is mediated predominantly by the CRLF1 moiety. The tripartite signaling complex formed by CRLF1, CLCF1 and CNTFR also binds SORL1. Belongs to the IL-6 superfamily.