CXC ligand 9(CXCL9), also known as gamma interferon-induced mononuclear factor (MIG), is a small molecular weight cytokine belonging to the CXC chemokine family. It is closely related to two other CXC chemokines, CXCL10 and CXCL11, both of which interact with the chemokine receptor CXCR3 to exert their chemokine function. CXCL9 is involved in Th1 type inflammation and it has many functions, the main one being chemical attraction. Activated B cells, monocytes, CD8+ memory T cells, and CD4+Th1T cells all respond to CXCL9. CXCL9 also promotes the Th1 response by acting as an antagonist of the IL-4/Th2 response, which occurs by blocking the occurrence of Th2-associated chemokines (eotaxin), thereby limiting Th2 infiltration. CXCL9 also exhibits direct antimicrobial activity through its extended C-terminal. In hematopoiesis, CXCL9 is involved in the mobilization and migration of CD34+ stem cells, and inhibits the formation of erythroid and myeloid cell colonies.