CCL21 and systemic sclerosis: In ELISA2 CCL21 levels were higher in SSc-PAH patients (n=51) compared to SSc patients with no PH (n=60) by RHC (0.66 ± 0.46ng/ml vs. 0.38 ± 0.23 ng/ml, p=0.001) (Figure 4B, iii).