Characterization and expression analysis of an interferon-γ2 induced chemokine receptor CXCR3 in common carp (Cyprinus carpio L.)

• Carp CXCR3 is sequenced and is closely related to CXCR3a of other teleosts.
• Carp CXCR3 is involved in macrophage-mediated immune responses.
• IFN-γ2 stimulates CXCR3 gene expression in carp macrophages and granulocytes.
• CXCb chemokines may be putative ligands for CXCR3.

Chemokine and chemokine receptor signalling pairs play a crucial role in regulation of cell migration, morphogenesis, and cell activation. Expressed in mammals on activated T and NK cells, chemokine receptor CXCR3 binds interferon-γ inducible chemokines CXCL9–11 and CCL21.Here we sequenced the carp CXCR3 chemokine receptor and showed its relationship to CXCR3a receptors found in other teleosts. We found high expression of the CXCR3 gene in most of the organs and tissues of the immune system and in immune-related tissues such as gills and gut, corroborating a predominantly immune-related function. The very high expression in gill and gut moreover indicates a role for CXCR3 in cell recruitment during infection. High in vivo expression of CXCR3 at later stages of inflammation, as well as its in vitro sensitivity to IFN-γ2 stimulation indicate that in carp, CXCR3 is involved in macrophage-mediated responses. Moreover, as expression of the CXCR3 and CXCb genes coincides in the focus of inflammation and as both the CXCb chemokines and the CXCR3 receptor are significantly up-regulated upon IFN-γ stimulation it is hypothesized that CXCb chemokines may be putative ligands for CXCR3.