Abstract: Recent findings suggest that the gut microbial communities have a close relationship with human health. The
immune system of infants is not fully functional at birth, and the gut microbiota is not stable, rendering them highly
susceptible to infections. It is considered that human milk is the best diet for the newborn, since it contains a wide range of
nutritional and immune components. This review summarizes the impact of the microbiota, nutrients, immune cells and immune
components in human milk on the development of the intestinal microflora and immune system of infants and the relationship
between the gut microbiota and atopic diseases. We expect that this paper will provide scientific evidence for reducing the risk of
infections in infants and preventing diseases, as well as provide insights into how to improve infant formula.

Key words: human breast milk, infant formula, infant immune system, gut microbiota