Tag Archives: immune cells

Breastfed babies have better immune systems. Here’s why

Credit: SnappyGoat.

It is an established medical fact that breastfeeding offers long-term positive medical benefits to babies, which can extend well into adulthood. For instance, breastfed babies are less likely to develop asthma, obesity, and autoimmune disease later in life compared to babies who are exclusively fed formula. Now, a new study reveals new insights into the biological mechanisms that may explain these immunological benefits.

More abundant immune cells

Breast milk contains over 200 different ingredients, including protein, fat, carbs, vitamins, minerals, enzymes, and hormones, although the exact composition will vary from mother to mother and even from one feeding session to another throughout the day.

According to the WHO, breast milk is the natural first food for babies, providing all the energy and nutrients that an infant requires for the first half-year of life. Breast milk continues to be an important part of an infant’s diet, providing half of their nutritional needs during the second half of the year, and one-third during the second year of life.

Breastfeeding transmits elements of the mother’s own microbiome and immune system, providing probiotics to support the growth of beneficial bacteria and kickstarting a baby’s microbiota. The mother transfers her antibodies to her baby through breast milk, and this is particularly true of colostrum, the first milk. For instance, breast milk is high in immunoglobulin A (IgA), which protects the baby from getting sick by forming a protective layer around the nose, throat, and digestive system.

In a new study published this week in the journal Allergy, researchers at the University of Birmingham have discovered that regulatory T cells — a specific type of immune cell which plays a role in regulating or suppressing other cells in the immune system — expand in the first three weeks of life in breastfed babies and are twice as abundant as in formula-fed babies.

According to the authors, these cells control the baby’s immune response so it doesn’t go overboard when it comes into contact with maternal cells transferred through breastmilk, thereby reducing inflammation.

What’s more, the researchers also noticed that bacteria called Veillonella and Gemella, known to support the function of regulatory T cells, are more abundant in the gut of breastfed babies.

“The influence of the type of milk received on the development of the immune response has not previously been studied in the first few weeks of life,” said senior author Gergely Toldi, a researcher at the University of Birmingham and consultant neonatologist at Birmingham Women’s and Children’s NHS Foundation Trust.

“Prior to our research the outstanding importance and the early involvement of this specific cell type in breastfed babies was unknown. We hope this invaluable new insight will lead to an increase in rates of breastfeeding and will see more babies benefit from the advantages of receiving breastmilk.”

“Furthermore, we hope for those babies who are formula-fed, these results will contribute to optimizing the composition of formula milk in order to exploit these immunological mechanisms. We are very grateful for the mums and babies who contributed to this special project.”

Cytokine storm and T cells might be important targets for COVID-19 antiviral treatments

Scanning electron micrograph of a human T lymphocyte (also called a T cell). Credit: NIAID

The worst outcomes of COVID-19 seem to be predicated more on whether or not the virus triggers an overreaction of the immune system rather than the infection itself. New research suggests that cytokine storms may lower T cell counts, a type of white blood cell that plays an important role in immune responses, thereby affecting disease severity.

When the immune system is too much of a good thing

Cytokines are small proteins released by many different cells in the body, including those of the immune system where they coordinate the body’s response against infection and trigger inflammation.

It is through the release of these molecules that immune cells are able to communicate with one another. Once released, the cytokines typically trigger localized inflammation, which is a physiological response by the body that aims to destroy the pathogen. 

Sometimes, however, the immune system overreacts during an infection, triggering the release of more cytokines than necessary and the recruitment of more white blood cells, which, in turn, produce even more cytokines. It’s a positive feedback loop that can lead to severe complications and life-threatening organ failure.

Doctors refer to this overreaction as a “cytokine storm”. In the context of COVID-19, cytokine storms seem to be associated with severe deterioration of the lungs, and perhaps other organs.

In a new study published in the journal Frontiers in Immunology, Chinese researchers found that cytokine release can drive the depletion and exhaustion of T cells.

Their investigation was prompted by the observation that patients with COVID-19 had very low numbers of lymphocytes, white blood cells that include T cells.

“We should pay more attention to T cell counts and their function, rather than respiratory function of patients,” said author Dr. Yongwen Chen of Third Military Medical University in China, adding that “more urgent, early intervention may be required in patients with low T lymphocyte counts.”

Chen and colleagues examined 522 COVID-19 patients and 40 healthy controls. Lymphocyte counts were recorded for 499 patients, 76% of whom had abnormally low total T cell levels.

The most severe cases who were admitted to intensive care units (ICU) had lower T cell counts than non-ICU cases. Likewise, those over the age of 60 had lower levels of T cells — this age group is particularly at risk of COVID-19 morbidity.

What’s more, the T cells that did circulate were ‘exhausted’, in the sense that they did not function at full capacity. In addition to increasing the risk of COVID-19 complications, T cell exhaustion is linked to secondary infections, which can be common in a hospital setting.

In the future, Chen and colleagues want to find finer subpopulations of T cells in order to paint a more accurate picture of their role in COVID-19 prognosis.

Importantly, there are many different types of cytokines, classified by the types of immune cells that release them. Each such cytokine may trigger a distinct response when binding to a receptor. For instance, some actually decrease inflammation rather than increasing it. It is therefore paramount to understand which cytokines are released in response to the coronavirus infection.

The findings might also spur drug discovery that promotes T cell production and boosts their function.

Tocilizumab, an existing immunosuppressive drug, might be effective in this context although it hasn’t been investigated yet in the context of COVID-19. The antiviral treatment Remdesivir may also prevent T cell exhaustion.