CXCR3 and systemic sclerosis: To investigate the effect of sildenafil on CXCL-9, -10 and -11 receptor localization in a pro-oxidant condition, we performed an immunofluorescence experiment for CXCR3 on non-permeabilized healthy and SSc fibroblasts treated with 100 μM H2O2 for 1 h in the presence or absence of sildenafil 1 μM.