CXCL9 and dry eye syndrome: Several studies in dry eye patients have demonstrated elevated levels of tear chemokines , such as macrophage inflammatory protein 1 alpha/chemokine (C-C motif) ligand 3 (MIP-1α/ CCL3), macrophage inflammatory protein 1 beta/chemokine (C-C motif) ligand 4 (MIP-1β/CCL4), RANTES/CCL5, Fractalkine/chemokine (C-X3-C motif) ligand 1 (CX3CL1), chemokine (C-X-C motif) ligand 9 (CXCL9), CXCL10, CXCL11 and monocyte chemoattractant protein 1/ chemokine (C-C motif) ligand 2 (MCP-1/CCL2), which are critical for function of monocytes and T-lymphocytes (43,46,48,52,63,76).