CD79A and selective IgA deficiency disease: IgA can target multiple microbial antigens, including LPS, proteins, flagellin and virulence factors (exotoxins), from pathogenic microbes; therefore, IgA is critical for maintaining a symbiotic balance between the microbiota and the immune system.55–58 In addition, gut microbiota alterations were also observed in humans with IgA deficiency.59–61 Conversely, gut microbiota commensals have also been reported to regulate IgA levels.