Chemokine (C-X-C motif) ligand 11 (CXCL11) is a small cytokine belonging to the CXC chemokine family. It is also commonly called Interferon-inducible T-cell alpha chemoattractant (I-TAC). There have been 17 different C-X-C chemokines described in mammals, that are subdivided into two categories, those with a specific amino acid sequence (or motif) of glutamic acid-leucine-arginine (or ELR for short) immediately before the first cysteine of the C-X-C motif (ELR-positive), and those without an ELR motif (ELR-negative). ELR-positive C-X-C chemokines specifically induce the migration of neutrophils, and interact with chemokine receptors CXCR1 and CXCR2. C-X-C chemokines that lack the ELR motif are chemoattractant for lymphocytes.
CXCL9 (MIG), CXCL10 (IP-10), and CXCL11 (I-TAC) are homologous, interferon-inducible members of the CXC chemokine family that lack the tripeptide structure/function motif Glu-Leu-Arg (ELR) important in neutrophil chemoattraction. As such, these interferon-inducible ELR-negative CXC chemokines signal through a common receptor, CXCR3, to facilitate selective recruitment of mononuclear leukocytes, natural killer cells, and plasmacytoid dendritic cells to sites of inflammation.