Increased frequency of circulating CD19+CD24hi CD38hi B cells with regulatory capacity in patients with Ankylosing spondylitis (AS) naive for biological agents

Our objective was to study the frequency of circulating CD19+CD24(hi) CD38(hi) B cells (Breg) in AS patients. To this end, peripheral blood was drawn from AS patients naive for TNF blockers (AS/nb) (n = 42) and healthy controls (HC) (n = 42). Six patients donated blood for a second time, 6 months after initiating treatment with anti-TNF alpha drugs. After isolation by Ficoll-Hypaque, PBMCs were stained with antibodies to CD3, CD4, CD19, CD24, and CD38, and examined by cytometry. For functional studies, total CD19+ B cells were isolated from PBMCs of 3 HC by magnetical sorting. Breg-depleted CD19+ B cells were obtained after CD19+ CD24(hi)CD38(hi) B cells were removed from total CD19+ cells by cytometry. Total CD19+ B cells or Breg-depleted CD19+ B cells were established in culture and stimulated through their BCR. Secretion of IFN. was determined by ELISA in culture supernatants. When compared with HC, AS/nb patients demonstrated a significantly increased frequency of Breg cells, which was independent of disease activity. Anti-TNF alpha drugs induced a significant reduction of circulating Breg numbers, which were no longer elevated after six months of treatment. Functional in vitro studies showed that the secretion of IFN. was significantly higher in Breg-depleted as compared with total CD19+ B cells, indicating that Breg can downmodulate B cell pro-inflammatory cytokine secretion. In summary, an increased frequency of circulating CD19+ CD24 hi CD38 hi B cells is observed in AS/nb patients, that is not related with disease activity; anti-TNF alpha drugs are able to downmodulate circulating Breg numbers in AS.