Human milk IgA promotes normal immune development by limiting Th17-inducing in the infant gut.

The gut microbiota is highly dynamic during the first year of life and plays a crucial role in immune development. Breastfeeding is known to support infant health, but the contributions of the numerous breastmilk components to gut microbiota and immune maturation remain unclear. Secretory IgA (SIgA), the most abundant antibody in human milk, is a key modulator of gut microbiota composition.