IGHA1 and IgA glomerulonephritis: Our previous basic research indicates that cytotoxin-associated gene A (CagA) of H. pylori increases secretion of serum immunoglobulin A1 (IgA1) and induces the underglycosylation of IgA1 through promoting the proliferation of B lymphocytes [8], in which underglycosylated IgA1 is well known as one of the key factors causing IgA nephropathy.