Differential effects of IFN-α and IFN-γ on upregulation of IFN-inducible chemokines CXCL9, CXCL10 and CXCL11.

2149 INTRODUCTION: Despite the presence of tumor Ag-specific T cells in the periphery of vaccinated patients, melanoma evades immune-mediated destruction. Optimizing T cell trafficking is essential to immunotherapy and may be facilitated by enhanced chemokine receptor interactions. CXCR3 ligands (CXCL9-11) are known as IFN-inducible chemokines, but the effects of IFN-α compared with IFN-γ on these three chemokines are not known.
 METHODS: Peripheral blood from 8 normal donors was incubated at 37 oC for 48h with clinically appropriate doses of either IFN-α (1x105 IU/ml) or IFN-γ (3.9 x105 IU/ml) and supernatants were assayed for CXCR3 ligands and for their ability to induce migration of activated T cells. Transwell chambers with 8μm untreated membranes were used. Antigen-stimulated human T cells were placed in the upper chamber and supernatants from IFN-treated PBL were diluted to 10% and placed in the lower chamber. The assay was incubated at 37oC for 4h and the cells in each chamber were counted. Control migration assays were run in parallel with the same activated T cell and supernatants from untreated PBLs.
 RESULTS: Both IFN-γ and IFN-α increased the production of CXCR3 ligands from PBL of normal donors (cumulative levels 614,147 and 909,223 pg/ml, respectively, vs. 4,321 for control). IFN-γ was dominant in increasing CXCL9 (MIG) in all 8 patients (mean 300,989 pg/ml vs. 404 pg/ml for IFN-γ and IFN-α, respectively). There was a balanced effect of IFN-γ and IFN-α on CXCL10 (IP-10, >500,000 pg/ml each) and IFN-α had a dominant effect on CXCL11 (I-TAC) in 7 out of 8 patients (87.5%; 32,636 for IFN-α vs. 21,329 pg/mL for IFN-γ). There were wide variations in migratory effects caused by IFN-induced supernatants from different normal donors (2.7%-62.5% of cells migrated). The percentage of cells that migrated under each treatment condition was calculated for each subject and the differences in these percentages were computed as alpha minus control and gamma minus control. The means of these values were averaged over all subjects and were 0.18 (-0.25, 0.61) and 0.10 (-0.06, 0.26) for the IFN-α and -γ differences, respectively. Interestingly, these variations were not explained by the measured levels of chemokines CXCL9-11.
 CONCLUSIONS: Chemokines CXCL9, CXCL10, and CXCL11 are induced by type 1 interferons, but there is striking differential susceptibility to IFN for each chemokine. The chemokine-enriched supernatants of IFN-treated mononuclear cells induce migration of antigen-activated human T cells. Preliminary data suggest that some migration effects of IFN-induced supernatants cannot be explained fully by the known IFN-inducible chemokines, raising the question of whether other chemokine-chemokine receptor interactions are affected by type I IFNs in a way that alters T cell trafficking. Better characterization of these interactions may provide new tools to improve immune-mediated therapy of cancer.