Figure 1.

Occurrence and levels of immunoglobulin (Ig)G proteinase 3‐ anti‐neutrophil cytoplasm antibodies (PR3‐ANCA) (a), secretory IgA (SIgA) PR3‐ANCA (b), and IgA PR3‐ANCA (c) in sera from patients diagnosed with ANCA‐associated vasculitis (AAV). Western blot for secretory component (d). IgA and IgG were purified from a serum sample taken from a double‐positive AAV patient and were then subjected separately to affinity purification on a PR3‐column. Anti‐secretory component reactivity was detected only in the IgA fraction. NHS = normal healthy subjects; IgAN = IgA nephropathy; IgAV = IgA vasculitis.