Chemokine (C motif) ligand (XCL1) is a small cytokine belonging to the XC chemokine family that is also known as lymphotactin. It is found in high levels in spleen, thymus, intestine and peripheral blood leukocytes, and at lower levels in lung, prostate gland and ovary. it shows little or no expression in colon and testis. Lymphotactin is chemotactic for CD4+ and CD8+ T cells but not for monocytes, and induces a rise in intracellular calcium in peripheral blood lymphocytes.

Cellular sources for XCL1 include activated thymic and peripheral blood CD8 T cells. This chemokine attracts T cells. In humans, XCL1 is closely related to another chemokine called XCL2, whose gene is found at the same locus on chromosome 1. XCL1 induces it chemotactic function by binding to a chemokine receptor called XCR1.