Interferon gamma inducible protein 10

Interferon gamma inducible protein 10 kDa (IP-10), also classified as CXCL10, is a chemokine produced by T cells, monocytes, endothelial cells and keratinocytes after stimulation with IFN-γ. The chemokine is highly inducible and belongs to the C-X-C or alpha subfamily of chemokines functioning as an important chemoattractant for activated T cells, monocytes and NK cells.

Expression of IP-10 is seen in many Th1-type inflammatory diseases, where it is thought to play an important role in recruiting activated T cells to sites of inflammation. Although IP-10 was named as a protein inducible by IFN-γ, other agents including LPS, IL-1α, IL-6, TNF-α, IFN-α and IFN-β were also found to induce IP-10 expression in vitro. In addition, IP-10 mRNA was expressed in IFN-γ knockout mice, confirming that IFN-γ is not absolutely necessary for in vivo IP-10 gene expression.

Figure This is a structure of IP-10 created using the data from Protein Data Bank (PDB: 1o7z).

IP-10 is structurally and functionally related to the chemokine MIG (Monokine induced by gamma interferon) also named CXCL9 and IFN-inducible T cell alpha chemoattractant (I-TAC, CXCL11). All three chemokines (induced by IFN-γ) direct migration and stimulate the adhesion of activated T cells and NK cells by activating the same receptor: CXCR3, a G protein-coupled receptor. Experimental data have shown that IP-10, MIG and I-TAC exhibit unique expression patterns in several skin diseases including psoriasis, supporting the concept that all three chemokines have nonredundant functions in vivo. Despite its well-described function of recruiting leukocytes to sites of inflammation, IP-10 also plays a role in the generation and function of effector cells.  For instance, IP-10 augments IFN-γ release from T cells following stimulation with environmental antigens like domestic cat and dust mites antigens (which commonly elicit cytokine responses in nonallergic subjects).