Patients with active GPA (n = 18) showed a significantly increased percentage of circulating IL-17A+ T cells compared to HC (n = 14) (% of CD4+ T cells = 1.7 ± 1.4% vs. 0.7 ±0.3%, P = 0.006 (Figure 1A, B), while there was no difference in IFNγ (14.5 ± 9.9% vs. 17.7 ± 7.9%, P = 0.17), or IL-4-producing CD4+ T cells (5.6 ± 3.3% vs. 4.9 ± 2.1%, P = 0.7). Here, CD4 is linked to granulomatosis with polyangiitis.