Notably, an expansion of the CD27+CD38++ B cell subset was identified as a biomarker for relapse prediction in anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) [29], humoral autoimmune diseases involving small to medium-sized blood vessels [1]. Here, CD27 is linked to anti-neutrophil cytoplasmic antibody-associated vasculitis.