Distribution of circulating T follicular helper cell subsets is altered in immunoglobulin A vasculitis in children

Immunoglobulin A vasculitis (IgAV) is the most common vasculitis in children. Previously, we demonstrated that patients with IgAV show abnormal proliferation of cluster of differentiation (CD)4+C-X-C chemokine receptor type (CXCR)5+ follicular helper T (Tfh) cells. Here, we explored the status of Tfh cell subsets and plasma cytokine levels in patients with IgAV. CD4+CXCR5+CD45RA-, CD45RA-CXCR3+CCR6-, CD45RA-CXCR3-CCR6-, CD45RA-CXCR3-CCR6+, and CD45RA-CXCR3+CCR6+ Tfh cell fractions and plasma concentrations of interferon-γ, interleukin (IL)-4, and IL-17A were evaluated by flow cytometry and a flow cytometric bead array, respectively, in 30 patients with IgAV and 15 healthy controls (HCs). Tfh2 and Tfh17 cell fractions were larger and the Tfh2+Tfh17/Tfh1 ratio and plasmaIL-4 and -17A levels were higher in patients with IgAV than in the HCs. Only Tfh1 cell counts were reduced in the abdominal subtype. The elevations in Tfh2 and Tfh17 cell counts and plasma IL-4 levels were abrogated by treatment. Tfh2 cell number was positively correlated with serum IgA and plasma IL-4 levels, but negatively correlated with the serum C4 concentration, while Tfh17 cell number was positively correlated with the serum IgA level and Tfh2 cell counts. Abnormally high numbers of Tfh2 and Tfh17 cells are linked to the occurrence and development of IgAV, but are not specific to the abdominal type. Only Tfh1 cells play a critical role in abdominal-type IgAV.