Circulating CD24 hi CD38 hi regulatory B cells correlate inversely with the Th EM 17 cell frequency in granulomatosis with polyangiitis patients.

Objectives To investigate whether there is a direct relation between expanded proportions of Th17 effector memory (Th_EM17) cells and regulatory B cells (Bregs) in peripheral blood of granulomatosis with polyangiitis (GPA) patients. Methods Frequencies of Bregs and Th_EM17 cells, as well as Th_EM1 cells, were determined by flow cytometry in blood samples from 42 GPA patients in remission and 18 matched healthy controls (HCs). The Breg frequency was defined as CD24^hiCD38^hiCD19⁺ cells. Th_EM17 cells were defined as CCR6⁺CXCR3^-CCR4⁺ cells and Th_EM1 cells as CCR6^-CXCR3⁺CCR4^- cells within the CD3⁺CD4⁺CD45RO⁺CCR7^- population. In addition, CD3⁺CD4⁺ Th cells from 9 GPA patients were co-cultured in vitro with either total B cells or a Breg-depleted B cell fraction. Cultured cells were stimulated with Staphylococcus Enterotoxin B (SEB) and CpG-oligodeoxynucleotides (CpG-ODN). Th17- (IL-17⁺) and Th1 cell (IFNγ⁺) frequencies were determined at baseline and day 5 upon restimulation with phorbol myristate acetate (PMA) and Ca-I. Results A decreased Breg frequency was found in treated GPA patients, whereas an increased Th_EM17 cell frequency was observed in treated and untreated GPA patients compared with HCs. Additionally, a decreased Th_EM1 cell frequency was seen in untreated GPA patients compared with HCs. In untreated GPA patients circulating Breg frequencies correlated negatively with Th_EM17 cells (r = −0.533; P = 0.007) and positively with Th_EM1 cells (r = −0.473; P = 0.015). The co-culture experiments revealed a significant increase in the frequency of IL-17⁺ Th cells in Breg-depleted samples (median: 3%; range: 1–7.5%) compared with Breg-undepleted samples (P = 0.002; undepleted samples median: 2.1%; range: 0.9–6.4%), whereas no difference in the frequency of IFNγ⁺ Th cells in Breg-depleted cultures was observed (undepleted median: 11.8%; range: 2.8–21% vs Breg-depleted median: 12.2%; range: 2.6–17.6%). Conclusion Bregs modulate Th_EM17 responses in GPA patients. Future studies should elaborate on clinical and therapeutical implications of the Breg-Th17 interaction in GPA patients. [ABSTRACT FROM AUTHOR]