Human milk is a highly complex biological fluid composed of numerous components that perform diverse and essential roles in infant development. Scientific research continues to reveal new functions and mechanisms associated with its bioactive elements. The immune system of a breastfed infant can be significantly influenced by human milk, as it contains immunological factors that actively interact with the infant’s developing immune responses. In addition to enhancing vaccine effectiveness and supporting immune maturation, breastfeeding may sometimes contribute to the modulation or suppression of certain immune reactions, including transplant rejection and the risk of developing specific autoimmune disorders such as type 1-diabetes. Breastfeeding appears to provide the newborn with optimal nutrition, reducing the risk of vitamin A deficiency and supporting an appropriate and well-regulated immune response. Moreover, the regulation of anti-inflammatory properties and the establishment of healthy gut microbiota through breastfeeding further increase the likelihood that the infant will develop a balanced and properly functioning immune system. Nevertheless, the precise roles of growth factors, cytokines, idiotypic and anti-idiotypic antibodies, along with other anti-inflammatory components present in maternal milk, in shaping the infant’s immune system still require further detailed investigation and ongoing scientific research.