In complex with CLCF1, forms a heterodimeric neurotropic cytokine that plays a crucial role during neuronal development (By similarity). Plays a role in the initiation and/or maintenance of suckling in neonatal mice (PubMed:10359701). May also play a regulatory role in the immune system (By similarity). Forms covalent di- and tetramers. Forms a heteromeric complex with cardiotrophin-like cytokine CLCF1/CLC; the CRLF1-CLCF1 complex is a ligand for the ciliary neurotrophic factor receptor/CNTFR. The CRLF1-CLCF1 heterodimer, as well as tripartite signaling complex formed by CRLF1, CLCF1 and CNTFR bind SORL1 (via N-terminal ectodomain); within this complex, the interaction is mediated predominantly by the CRLF1 moiety. Widely expressed in the embryo. Not detected in the brain of adult mice. The WSXWS motif appears to be necessary for proper protein folding and thereby efficient intracellular transport and cell-surface receptor binding. Belongs to the type I cytokine receptor family. Type 3 subfamily.