Increased frequency of PD-1(hi)CXCR5(-) T cells and B cells in patients with newly diagnosed IgA nephropathy

Recent research has identified a population of PD-1(hi)CXCR5(−) ‘peripheral helper’ T (Tph) cells that simulate plasma cell differentiation by interactions between IL-21 and SLAMF5. However, the alteration of circulating Tph and CD138(+) B in IgA nephropathy (IgAN) remains poorly understood. Flow cytometry analysis was used to measure the frequency of circulating PD-1(hi)CXCR5(−) T cells and CD138(+) B cells in 37 patients with IgAN and 23 healthy controls (HCs). Estimated glomerular filtration rate (eGFR), 24 h urinary protein and serum cytokine concentrations were measured. The percentage of different subsets of circulating PD-1(hi)CXCR5(−) T cells and CD138(+) B cells were significantly higher in patients with IgAN compared to HCs. Pretreatment, the percentage of different subsets of circulating PD-1(hi)CXCR5(−) T cells and CD138(+) B cells were negatively correlated with eGFR, the percentage of circulating CD138(+) B cells was positively correlated with 24-h urinary protein concentration, and the percentage of circulating PD-1(hi)CXCR5(−), CD28(+) and ICOS(+) T cells. Posttreatment, the percentage of different subsets of circulating PD-1(hi)CXCR5(−) T cells and CD138(+) B cells and serum IL-21 concentration were significantly reduced. Different subsets of circulating PD-1(hi)CXCR5(−) T cells contribute to the progression and pathogenesis of IgAN by regulating the differentiation of CD138(+) B cells through a combination of surface molecules.