Th17 cells in cross-sectional and longitudinal analysis. (A) Representative fluorescence activated cell sorter (FACS) plots of a volunteer healthy control (HC) and a patient with granulomatosis with polyangiitis (GPA). Plots are gated on CD3+CD8neg T cells and 40,000 events are shown in each graph. (B) The percentage of Th17 cells was higher in quiescent GPA than in HC. Active GPA patients showed a significantly increased Th17 cell fraction compared to HC and did not differ from quiescent GPA. Mean values are indicated by the horizontal line, and error bars represent the SD. (C) Seven patients were first assessed during the active phase of disease and then again after remission had been achieved. The dotted line represents the mean value in the HC. *P < 0.05, **P < 0.005.