CXCL11, also known as I-TAC, SCYB9B, H174 and beta -R1, is a non-ELR CXC chemokine. CXCL11 cDNA encodes a 94 amino acid (aa) residue precursor protein with a 21 aa residue putative signal sequence, which is cleaved to form the mature 73 aa residue protein. CXCL11 shares 36% and 37% amino acid sequence homology with IP-10 and MIG (two other known human non-ELR CXC chemokines), respectively. CXCL11 is expressed at low levels in normal tissues including thymus, spleen and pancreas. The expression of CXCL11 mRNA is radically up regulated in IFN-gamma and IL-1 stimulated astrocytes. Moderate increase in expression is also observed in stimulated monocytes. CXCL11 has potent chemoattractant activity for IL-2 activated T cells and transfected cell lines expressing CXCR3, but not freshly isolated T cells, neutrophils or monocytes.