CXC ligand 9 (in short: CXCL9 or MIG for English monokines induced by interferon-gamma ) is a protein in mammals. It forms with CXCL10 and CXCL11, a group of homologous chemokines ( messengers). These neurotransmitters are produced in the context of an inflammatory reaction mainly of macrophages. They play a role in the activation of T lymphocytes and thus the activation of the adaptive immune system.


Macrophages secrete the neurotransmitter CXCL9 after stimulation with the proinflammatory cytokine interferon - γ. Moreover, CXCL9 can be secreted to a lesser extent by neutrophilic granulocytes. For this, a stimulation with interferon - γ but not enough. The anti-inflammatory interleukins IL -4 and IL -10 suppress the expression of CXCL9 in neutrophils. The chemokine binds to G protein-coupled receptor CXCR3 ( CXC receptor 3). This CXCR3 presenting cells of the immune system such as TH1 lymphocytes and NK cells are capable of chemotactic to follow a concentration gradient of CXCL9.

Locus and classification

The CXCL9 gene encoding ScyB9 (small secreted cytokine B) is located close to the genes for CXCL10 and CXCL11 in the chromosomal region 4q21. The location away from the comprehensive significantly more genes CXC chemokine cluster on 4q13 demonstrates the greater affinity of these three chemokines with each other. At the of ScyB9 encoded propeptide N -terminal 22 amino acids is cleaved off a signal sequence. The secreted form contains 103 amino acids with a calculated molecular mass of 11.7 kDa. Because of the lack of glutamyl- leucyl -arginine motif ( ELR) is CXCL9 as a non- ELR CXC chemokine classified.

Polarization of the acquired immune response

CXCL9, CXCL10 and CXCL11 bind to the common receptor CXCR3. This is expressed predominantly by TH1 lymphocytes upon activation with IL -2 and natural killer cells. Unlike other chemokines are CXCL9, CXCL10, CXCL11, and do not enable the position leukocytes have more than one receptor. About the binding of the CC chemokine receptor CCR3 they prevent activation of Th2 lymphocytes present this receptor mainly. In this way promotes CXCL9, CXCL10 and CXCL11 as a polarization in favor of pro-inflammatory, Th1 -mediated immune response.