Treating peripheral blood mononuclear cells (PBMCs) from GPA patients with B cell activating factor (BAFF) and IL-21 increases ANCA production, which is further exacerbated with oligodeoxynucleotides containing CpG motifs, a pathogen-associated immunostimulant [34]. This evidence concerns the gene TNFSF13B and granulomatosis with polyangiitis.