Involved in the initial immune cell clustering during inflammatory response and may regulate chemotactic activity of chemokines. May play a role in melanocortin signaling pathways that regulate energy homeostasis and hair color. Low-affinity receptor for agouti (By similarity). Has a critical role in normal myelination in the central nervous system.
Isoform 2 is detected in plasma (at protein level). Expressed and secreted by activated T lymphocytes. Expressed at low to moderate levels in peripheral blood leukocytes, spleen, lymph node, tonsil, bone marrow and fetal liver. At very low levels found in thymus. Isoform 2 is the major isoform in peripheral blood leukocytes.