What is the immune factor in breastmilk that helps develop the mucosal barrier in infants?

The immune factor in breastmilk that plays a critical role in the development of the mucosal barrier in infants is immunoglobulin A (IgA). IgA is the primary antibody found in secretions, such as saliva, tears, and importantly, breastmilk.

In breastmilk, IgA exists predominantly as secretory IgA (sIgA), which is specially designed to be resistant to degradation by enzymes and to prevent pathogens from adhering to the intestinal mucosa. This helps to protect the infant's gut before their own immune system is fully developed. The presence of IgA in breastmilk contributes to the maturation of the neonatal immune system and helps establish a healthy gut microbiota, providing a crucial first line of defense against infections.

Other immunoglobulins, such as IgM, IgG, and IgE, also play roles in immune response but are not primarily associated with the mucosal barrier in the context of breastmilk. IgM is involved in the early stages of the immune response, IgG is the most prevalent antibody in the bloodstream and provides long-term immunity, while IgE is primarily involved in allergic reactions and responses to parasites. Therefore, IgA stands out as the key factor in developing the mucosal barrier in infants