I-TAC (Interferon-inducible T-cell α Chemoattractant), also known as CXCL11, is a chemokine belonging to the CXCL subfamily. Along with Interferon-γ induced Protein 10 kDa and Monokine Induced by Interferon-γ, I-TAC is strongly up-regulated by Interferon-γ and binds to the G-protein coupled receptor CXCR3. The expression of CXCR3 is associated with Th1-mediated immune responses and mediates chemotaxis of Th1 cells. I-TAC induces, maintains, and amplifies the inflammatory reactions, and sustains chronic immune responses against self-antigens. Although CXCR3 was thought to be the exclusive receptor of I-TAC initially, more evidence has shown that I-TAC can also bind to CXCR4 and CXCR7, and that I-TAC plays important roles in tumor development and angiostasis. 
Recombinant human I-TAC/CXCL11 (rhI-TAC)  produced in E. coli is a single non-glycosylated polypeptide chain containing 74 amino acids. A fully biologically active molecule, rhI-TAC has a molecular mass of 8.4 kDa analyzed by reducing SDS-PAGE and is obtained by proprietary chromatographic techniques at ExCell Bio.