Enteromammary immune system

The enteromammary immune system refers to the pathway by which immune cells activated in the mother’s gut migrate to the mammary glands.

• This allows maternal exposure to microbes, food antigens, and pathogens in her intestine to influence the antibodies (especially secretory IgA) secreted into breast milk.

• This is a gut-to-breast immune link which provides targeted protection for the infant’s gut.

Maternal-infant immune system

The maternal-infant immune system is a broader term which includes all immunological interactions between mother and child.

This covers:

• Prenatal immunity (e.g., transplacental transfer of IgG antibodies).

• Postnatal immunity through breastfeeding (antibodies, immune cells, cytokines, oligosaccharides).

• Maternal microbiota - of the milk and the nipple-areolar complex - and other skin contact that help “train” the infant immune system.

The mammary immune system

The mammary immune system comprises immune cells, tissues, and molecular mechanisms which protect the mammary gland from infection and maintain tissue homeostasis. It also contributes to the transfer of immune factors, such as antibodies, into milk during lactation, providing passive immunity to offspring and supporting neonatal health.

Key components of the mammary immune system include macrophages (pictured in the photo at the top of this page), neutrophils, lymphocytes, and dendritic cells, which reside in the breast stroma or are recruited during challenges such as mastitis. These cells

• Identify and eliminate microbes which may be threatening to become dominant in a way that could cause pathology

• Produce cytokines, and

• Facilitate tissue repair.

The mammary immune system is particularly active during lactation, when the breast is in a heightened pro-inflammatory state.

Summary

Both the enteromammary system and the mammary immune system are overlapping components of the maternal-infant immune system. The maternal-infant immune system is an umbrella concept. The enteromammary pathway is a specific mechanism within it that explains how the mother’s gut experiences shape the immune factors in her milk. The mammary immune system is the immune activity in a woman's breast which protects her breast stroma and her milk, and also provides immune cells and factors in the milk to protect her infant.

The photo at the top of the page is of a macrophage, under microscopy.

Selected references

Guillen-Morales DdJ, Cruz-Cortes I, Sosa-Velazco TA, Aquino-Dominguez AS. The mother-infant symbiosis: a novel perspective on the newborn's role in protecting maternal breast health. Hygiene. 2025;5(46):https://doi.org/10.3390/hygiene5040046.