Association between Tfh and PGA in children with Henoch–Schönlein purpura

OBJECTIVE: The aim of this study was to investigate the roles of follicular helper CD4(+) T cells (Tfh) and serum anti-α-1,4-d-polygalacturonic acid (PGA) antibody in the pathogenesis of Henoch–Schönlein purpura (HSP). METHODS: ELISA was performed to determine serum PGA-IgA and PGA-IgG. Flow cytometry was utilized to determine the peripheral CD4(+) CXCR5(+) and CD4(+) CXCR5(+) ICOS(+) Tfh cells. Real-time PCR was conducted to determine the expression of Bcl-6 gene. Then the change of Tfh cells was analyzed, together with the association with the anti-PGA antibody as well as the roles in the pathogenesis of HSP. RESULTS: Compared with the cases with acute respiratory infection and elective surgery, the proportion of CD4(+) CXCR5(+) and CD4(+) CXCR5(+) ICOS(+) Tfh cells in the HSP group showed significant elevation (P < 0.001). A significant correlation was noticed between PGA-IgA and CD4(+) CXCR5(+) Tfh cells (r = 0.380 and P = 0.042) and CD4(+) CXCR5(+) ICOS(+) Tfh cells (r = 0.906 and P < 0.001). The expression of Bcl-6 in the HSP group showed no statistical difference compared with that in the acute respiratory infection and the surgery control (P < 0.05). CONCLUSION: Increased activity of Tfh cells, which is closely related to mucosal immunity, may be a major contributor in the elevation of PGA-IgA, and Tfh cells and PGA-IgA are closely related to the occurrence of HSP.