Babies who have a strong immune reaction in the first week of life seem to have triple the risk of developing an allergy or eczema by age 1, compared with those who don’t. But the long-term impact of this early immune response, now defined for the first time, seems to be modulated by the microbiome and how babies are fed. But at a talk at an immune conference in London earlier this month, Brodin challenged this idea.
He revealed that he and his colleagues have found that an immune response in the first week of life seems to have an oversized impact on how a baby’s immune system subsequently develops. How older siblings may shape sexual orientation via mother’s immune system In ongoing research, Brodin and his colleagues have been studying nearly 600 infants in Sweden, collecting and analysing blood and stool samples from the infants throughout their first year of life. The analysis revealed that about half the babies had what the researchers termed a strong “seeding” immune reaction during the first week of life, marked by high levels of inflammatory molecules such as interferon gamma, which activates immune cells.
The remaining infants had lower levels of these inflammatory molecules during the first week, which the team called a weak seeding reaction. Further analysis revealed that babies with a strong seeding reaction had substantially more Bacteroides bacteria in their gut than those who had a weak reaction. Babies can pick up these bacteria via interactions with their mother and family members, he says.
The researchers think the effects of the seeding reaction last for only about a week at the beginning of life because that is when the gut is especially leaky, enabling bacteria like Bacteroides to enter the bloodstream and activate immune cells. But the seeding reaction may have lasting effects: by sifting through the infants’ medical records, the researchers found that 39 per cent of those with a strong seeding reaction developed either eczema or a food allergy by age 1. In contrast, just 12 per cent of infants with a weak seeding reaction developed at least one of these conditions, which are caused by excessive inflammation.
Further analysis revealed that the infants with a strong reaction then followed one of three immune trajectories depending on two main factors: whether they were primarily fed breast or formula milk, and the abundance of bifidobacteria in their gut. For instance, 50 per cent of babies who had a strong seeding reaction and were breastfed – but had low levels of bifidobacteria – developed eczema or food allergies. Breastfed infants with high bifidobacteria levels were less likely to develop eczema or food allergies, with 25 per cent of them doing so.
Babies are born with the neural foundations for maths The researchers also found that 33 per cent of infants who had a strong seeding reaction and were fed formula milk developed eczema or an allergy by age 1. In the work presented at the conference, the team didn’t give details of bifidobacteria levels in the guts of these formula-fed babies. Brodin says the bifidobacteria may be important because they break down certain sugars in breast milk, known as human milk oligosaccharides (HMOs), to produce anti-inflammatory molecules called short-chain fatty acids.
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