IL7 and pulmonary arterial hypertension: First, we determined the plasma concentrations of immune-modulatory IL-7: Children with PAH had approximately 50% lower IL-7 concentrations in the SVC (6.61 ± 1.04 vs. 13.25 ± 1.10 pg/mL, p < 0.001), PA (6.77 ± 0.93 vs. 13.63 ± 1.55 pg/mL, p < 0.01) and AAO (6.62 ± 0.82 vs. 13.97 ± 1.58 pg/mL, p < 0.01) vs. in the corresponding sites of controls (Figure 1A).