CXCL9 is a small cytokine belonging to the CXC chemokine family that is also known as monokine induced by gamma interferon. It is closely related to two other CXC chemokines called CXCL10 and CXCL11, whose genes are located near the gene for CXCL9 on human chromosome 4. CXCL9, CXCL10 and CXCL11 all elicit their chemotactic functions by interacting with the chemokine receptor CXCR3. Recombinant human CXCL9 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.