CD79A and Recurrent upper respiratory tract infections: A connection between the mucosa-associated immune system and IgAN is indicated by the following: (1) a main clinical feature of IgAN is gross hematuria after an upper respiratory tract infection, and (2) the renal deposits of IgA consist of polymeric IgA1 and secretory IgA, which are mostly produced by the MALT [31,32,33].