Food allergies linked to overactive immune system at birth

One in every ten babies in Melbourne develops a food allergy during their first year of life. New research has found children who are born with overly active immune cells are more likely to develop allergies to milk, eggs, peanuts, wheat and other common foods. This finding could lead to future treatments for babies to prevent childhood food allergies.

We discovered changes in immune cells at birth that were associated with an increased risk of babies developing food allergies in the first year of age. In essence, these babies have immune systems that are “primed” for allergic disease by the time they are born.

Immune snapshot

The research was based on umbilical cord blood samples from the Barwon Infants Study, which followed mothers during pregnancy and their infants from birth to look at the environmental and genetic factors that influence immunity and allergy.

The blood from the umbilical cord showed us a snapshot of the baby’s immune system at the time of birth. In babies who developed food allergies we found immune cells called monocytes were more activated. This must have occurred either before or during birth.

Monocytes are less specialised cells of the immune system; let’s call them the “foot-soldiers” at the front line of defence against infections. As part of the study, we showed the hyperactive monocytes changed the “landscape” of the immune response by more specialised immune cells called T cells, driving the T cells to adopt characteristics we know are responsible for allergic reactions.

In babies in our study, these immune cell changes were associated with development of allergy to foods such as milk and egg, and later peanuts, wheat and other foods.

Allergy and immune disease increasing

In Australia, there has been a three-fold increase in hospital presentations due to food allergy over the last two decades and most of this increase has been among children under five years of age. Immune-related diseases more generally have also increased, including other allergies such as eczema and asthma, and type 1 diabetes, multiple sclerosis and inflammatory bowel disease.

Abnormal immune development during early life is likely to be relevant to each of these conditions. Food allergy is an ideal candidate to study as it is common, has an early onset and can be clearly defined.

The next step is to identify why these babies have hyperactive immune cells at birth. Are the immune cells activated because of the baby’s genes or are they activated at the time of birth or earlier in pregnancy, and how? While underlying genetic susceptibility to allergy may be a factor, the rising incidence of food allergy points to the environment as the major culprit.

We didn’t find any relationship to the mode of delivery (vagina versus elective or non-elective Caesarian), but there was a correlation with the duration of labour. However, duration of labour was not correlated with food allergy itself, emphasising that other factors post-birth must be at play.

A range of lifestyle and environmental factors (diet, nutrition, vitamins, exposure to infection, antibiotics and so on) that may modify immune cells in the body are under scrutiny. Many of these influence the mother’s microbiome, the collection of bacteria and other micoorganisms we all carry.

Establishment of colonies in the baby by the mother’s microorganisms at birth is critical in the development of the baby’s immune system. If we can understand what’s driving the activation of monocytes in the baby, we might be able to design lifestyle and environment modification strategies to lower the chances of babies being born with an increased risk of developing food allergy.

This study and its findings show how important it is to look at pregnancy and early life to understand why immune disorders such as allergies have increased in childhood and later.