CD79A and selective IgA deficiency disease: However, it is widely accepted that the main defect in individuals with SIgAD is a defect in the maturation from an IgA expressing (IgA+) B cell into an IgA secreting plasma cell that might be related to the process of alternative splicing of mRNA in IgA-secreting B cells and this results in the generation of membrane bound IgA+ B-cells but not secreted IgA antibodies (2–4, 6, 27, 82, 93).