Abstract: The invention is in the field of therapy of antibody deficiencies. Inventors demonstrate for the first time in both controls and IgA-deficient patients, systemic anti-microbiota IgG responses correlate with reduced inflammation suggesting that systemic IgG responses contribute to the gut microbiota confinement. Furthermore, SIgAd-associated inflammation is inversely correlated with systemic anti-commensal IgG responses, which may thus serve as a second line of defense. Altogether, these data suggest that systemic IgG and intestinal IgA cooperate in different body compartments to limit systemic pro-inflammatory pathways. As selective IgA deficient patients harbour elevated seric anti-commensal IgG levels, these findings suggest that in selective IgA deficiency, microbiota confinement is obtained at the price of a strong inflammatory response.