Immune factors in human milk

Human milk contains a wide spectrum of soluble immune compounds (immunoglobulins, cytokines, chemokines, and growth factors), which remain active once in the infant gastrointestinal tract and contribute to the immune protection and immune development of the infant’s naive immune system. Human milk composition is a genuine example of the dynamic maternal adaptation to the ever-changing needs of the breastfed infant. This fact is reflected by the variation in the composition of immune factors depending on several factors, such as genetic background, gestational age, time after birth, time of the day, geographical location, maternal diet, and the health status of both the mother and the infant. Current pasteurization methods in human milk banks affect some biologically active compounds present in human milk. In the past, the study of such soluble factors in human milk has been difficult because of their complexity, their relatively low concentrations, and the lack of specific procedures and reagents to quantify such agents in this cocktail-like biological fluid. However, the number of such compounds that have been detected in human milk is growing rapidly. Although the actual physiologic effects of each of these factors in the infant have not yet been elucidated completely, their presence seems to be extraordinarily relevant for infant and mammary health.