Previous animal models of Primary Antibody Deficiency (PAD) display severe dysbiosis and gut inflammation, which makes them incompatible to study a wide spectrum of PAD (e.g., most IgAD subjects display only mild dysbiosis and are asymptomatic). We would like to evaluate a novel mouse model of PAD and then perform microbiome transplant and IgA supplementation. The first objective is to evaluate the causal role of the microbiome in mediating PAD-associated disease. Our second objective is to apply an IgA supplement to reverse gut dysbiosis in symptomatic PAD and look at the microbiome changes caused by supplementation.