DYNAMICS of breastfeeding offer invaluable lessons that can be utilised for the universal benefit of infant nutrition.

Do we realise that the lactating mammary gland is a part of a specialised immune system?

When the mother starts producing milk, her mammary glands are empowered with immune activity as part of a specialised immune system, most definitely in the interest of the breastfeeding infant.

This system includes immunity from mucosal surfaces of the gastrointestinal, respiratory and renal systems, as well as the female reproductive systems and the eye.  These are the body’s first line defences against harmful agents.

By being a part of this, the lactating mammary gland is not isolated from early immunological information. It is enriched by mucosal immune signals from these areas of the body which can be transferred to mother’s milk to protect the breastfeeding infant. 

In those who can’t breastfeed and must rely on formula milk, mucosal immune responses of the mammary glands must be reproduced as closely as possible.

Factors that provide or stimulate such protective defences, through research, ensuring their safety, stability and bioavailability, must somehow be incorporated into it. 

Importance of an immune system at mucosal surfaces in infants

Mucous membranes are boundaries between us and our ever-changing environment.

They are sentinels at portals of entry where the air we breathe or the foods we ingest, first come into contact with the body. Air, food or water-borne microbes and allergens are an endless list of “invaders” that the mucosal system must ward off.

The mucosal immune system must protect and strengthen mucosal surfaces efficiently, yet cautiously, to avoid damage to delicate, immature mucosal barriers, especially in the infant.

In the gut, the role of the mucosal immune system is even more complex because both useful and harmful microbes can potentially exist.

Mucosal immune factors must defend against harmful microbes and must nurture useful microbes, which are important to physical and mental health. 

A perfect milk formula must integrate long lasting mucosal factors capable of fortifying mucosal barriers.

These mucosal factors must be able to successfully prevent or at least, reduce diseases transmitted through the polluted environment. It must also encourage and sustain a favourable gut eco-environment.

Features of breastmilk mucosal protection

Breastfeeding is regulated by lactogenic hormones and makes up for the newborn’s immune immaturity.

Secretory immunoglobulin‐A (sIgA) is the main type of specialised antibody in mucosal secretions.

It consists of four chains, the alpha heavy chain, the light chain, the joining chain and the secretory component. Its exceptional structure renders it resistant to digestion. Its levels in milk, together with other mucosal defences, are fine tuned to the changing needs of the developing infant.

The sIgA in breastmilk protects mucosal surfaces against harmful viruses, bacteria and parasites and in doing so, also guards mucosal integrity because of its lack of inflammation.

Goldman showed that immune cells in the gut are transformed to antibody‐producing cells in the breast and through this route, milk contains antibodies directed against harmful microbes from the mother’s gut.

The link between mother’s breasts and the gut also allows specific microbes to enter milk as a source of useful gut microbes to the baby.

Likewise, signals of mucosal immunity in mum’s respiratory tract can be transferred into milk with targeted antibodies in breastmilk such as in influenza virus infections.

The ideal milk formula will have to closely tweak the immune links in the breastfeeding dyad. Within the constraints of technology, formula milk must also provide targeted protection against airborne microbes and others, in a safe and stable manner in an unpredictable environment.

Holistic protection

Colostrum and breastmilk factors provide timely, passive immunisation, for general protection. Breastmilk may even actively immunize the nursing infant (through anti-idiotypes) for specific protection. Milk sIgA modifies some exaggerated immune responses to modulate protection (against allergies).

The lactating mammary glands integrating with mucosal immunity are enriched by mum’s immune experiences.

While methodologies in producing infant nutrition must constantly advance with time using breastfeeding as benchmark, natural mother-to-infant responses are virtually impossible to entirely emulate by technology alone. – July 16, 2020.

* Dr Prameela Kannan Kutty is a professor of paediatrics at the Universiti Pertahanan Nasional Malaysia.

* This is the opinion of the writer or publication and does not necessarily represent the views of The Malaysian Insight. Article may be edited for brevity and clarity.