Figure 1.

Adenosine deaminase 2 (ADA-2) levels in vasculitis. A, ADA-2 activity measured by spectrophotometric assay. ADA-2 activity was measured in serum from healthy controls (HCs; n = 6), monoallelic carriers (MCs; n = 6), and patients with deficiency of ADA-2 (DADA2; n = 6) from the National Institutes of Health (NIH) Clinical Center, and in serum from patients with idiopathic polyarteritis nodosa (PAN; n = 88) or granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA; n = 51). Among those with GPA/MPA, 16 patients had monoallelic ADA-2 variants, indicated by yellow and green circles, and 35 patients without a demonstrable variant were randomly chosen (open circles). B, ADA-2 activity measured by certified high-performance liquid chromatography (HPLC). ADA-2 activity was measured in serum from healthy controls (n = 6), monoallelic carriers (n = 6), and patients with DADA2 (n = 6) from the NIH Clinical Center, and in serum from patients with idiopathic PAN with biallelic variants (2VAR; n = 2), monoallelic variants (1VAR; n = 3), or no variant in ADA-2 (0VAR; n = 6, selected for low enzyme activity in A). Dashed lines show the upper limit of the reference range for patients with DADA2 (URP; 2.5 mU/ml) and the upper limit of the reference range for carriers (URC; 11.4 mU/ml), using HPLC. Bars show the mean ± SD. Subjects with 2 pathogenic or likely pathogenic variants are shown in red, those with 1 pathogenic or likely pathogenic variant are shown in yellow, those with 1 variant of unknown significance are shown in green, and those with no demonstrable variant are shown as open circles. * = P ≤ 0.05; ** = P ≤ 0.01 by Mann-Whitney U test. NS = not significant.