In vitro biologic activity of citrullinated CXCL11 in CXCR3 transfectants. Phosphorylated ERK1/2 (A) or PKB/AKT (B) were measured by specific ELISAs after stimulation of serum-starved CHO-CXCR3 cells for 5 minutes with CXCL11, CXCL11-Cit₆, or medium (control). Results represent the percentage ERK1/2 (□) and PKB/AKT (■) phosphorylation (mean ± SEM) compared with medium-treated cells (100%) from 3 or more independent experiments. Statistical analysis was performed using the Mann-Whitney test on paired values (*P < .05, **P < .01, ***P < .001 for comparison with control). (C) The increase of [Ca²⁺]_i (nM) in U87-CXCR3 cells was measured on stimulation with different doses (nM) of CXCL11 (♦) or CXCL11-Cit₆ (□). Values represent the mean (± SEM) increase of [Ca²⁺]_i (3-6 independent experiments) with a detection limit of 10 nM (…). Statistical analysis was performed using the Mann-Whitney test (‡P < .05, ‡‡P < .01 for comparison of authentic with citrullinated chemokine).