Moreover, the feeding modality shapes the trajectory of microbiota development and immune system maturation, with formula-fed infants exhibiting a more diverse microbiota profile, characterised by a higher proportion of anaerobic bacteria, in contrast to their breastfed counterparts, likely due to the dominance of Bifidobacterium. The gut microbiota substantially modulates immunological responsiveness through its impact on the IgA antibody production, which is the cornerstone of cellular humoral immune defence, impacting the risk of autoimmune diseases. This evidence concerns the gene CD79A and autoimmune disease.