In complex with CRLF1, forms a heterodimeric neurotropic cytokine that plays a crucial role during neuronal development (Probable). Also stimulates B-cells. Binds to and activates the ILST/gp130 receptor. 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 (PubMed:26858303). The CRLF1-CLCF1 heterodimer binds SORL1 (via N-terminal ectodomain); within this complex, the interaction is mediated predominantly by the CRLF1 moiety (PubMed:26858303). The tripartite signaling complex formed by CRLF1, CLCF1 and CNTFR also binds SORL1 (PubMed:26858303). Expressed predominantly in lymph nodes, spleen, peripheral blood lymphocytes, bone marrow, and fetal liver. The disease is caused by variants affecting the gene represented in this entry. Belongs to the IL-6 superfamily.