Although it is produced by B cells, IgA is continuously secreted in mass quantities, is often antigen-independent (and thus doesn’t require induction of an adaptive response), cross-reactive across many microbial antigens, and also functions as a barrier defense [37]; such IgA can, for example, alter establishment of gut commensals [41] or prevent infection by pathogenic pneumococci [42]. The gene discussed is CD79A; the disease is infection.