MPO and anti-neutrophil cytoplasmic antibody-associated vasculitis: In the current study, we did not find a significant correlation between the frequency of IgD-CD27hiCD38hi B cells and ANCA titers in AAV patients, mainly MPO-ANCA, for there is a striking preponderance of MPO-ANCA rather than PR3-ANCA in Chinese patients with AAV [28].