Chemokine (C-X-C motif) ligand 9 (CXCL9) also known as Monokine induced by gamma interferon (MIG) is a small cytokine belonging to the CXC chemokine family. It is closely related to two other CXC chemokines called CXCL10 and CXCL11, they all elicit chemotactic functions by interacting with the chemokine receptor CXCR3.
CXCL9 is involved in Th1-type inflammation. It has a number of functions, the principal being chemoattraction. Cells known to respond to CXCL9 include activated B cells, monocytes, CD8 memory T cells, and CD4 Th1 T cells. CXCL9 also promotes Th1 responses by serving as an antagonist to IL-4/Th2 responses. This occurs by blocking Th2-related chemokine (eotaxin), thus limiting Th2 infiltration. CXCL9 also demonstrates direct anti-microbial activity, apparently through its extended C-terminus. During hematopoiesis, CXCL9 is involved in the mobilization and migration of CD34 stem cells, and the suppression of colony formation of both erythroid and myeloid lineage cell types.