When immune systems couple up

2016-03-immune-couple-up

Your immune system becomes like your partner셲 when you cohabit.

Share and share alike. When you셱e in a relationship, you might well share sleeping habits, diets and exercise schedules with your partner. Now it seems your immune systems also converge when you live together.

Everyone셲 immune system is unique, varying in the number and type of immune cells and their activation states. This diversity is why the same flu virus can make one person ill for an afternoon, but can leave someone else bedridden for days.

Adrian Liston at the Catholic University of Leuven in Belgium and his colleagues have looked at blood samples from 670 healthy people aged between 2 and 86. For every person, the team counted the amounts of immune cells in each of 54 different activation states. The group then analysed further samples from a quarter of these volunteers over a six-month period.

The immune profiles tended to be remarkably stable, says the team, and even when disturbed, they returned to a similar baseline state. When people caught gastroenteritis, or had a flu vaccine, their immune systems were only temporarily perturbed before returning to normal.

This is reassuring, says Valerie O섵onnell at Cardiff University, UK. 쏷he immune system deals with the stressor and then recovers well.

In the family way

But Liston spotted an interesting pattern the immune systems of people who live together seem to be remarkably similar. 쏷here is a 50 per cent reduction in variation, which is an extremely profound effect, says Liston. 쏧t셲 a larger effect than you see over 40 years of ageing.

People in relationships tend to adopt similar diets and lifestyles, a phenomenon known as spousal concordance. The partner of a teetotal person is likely to drink less, for example. It is probable that some aspect of a couple셲 shared environment is the cause of their converging immune systems, says Liston.

There셲 evidence for a few potential culprits. Exposure to pollution can affect the immune system, and two people living together are likely to experience similar exposures. Holden Maecker of Stanford School of Medicine in California thinks the immune systems of cohabiting couples could be shaped by sharing common viruses with each other.

Microbial conduits

People who live together also seem to have similar collections of gut bacteria, which are important for immune functioning. This similarity could be influenced by the microbes found on household surfaces or in dust, or perhaps because of children. All the couples included in the study were parents, so their children could have acted as microbial conduits, says Liston.

쏧t셲 not particularly nice to imagine, but the easiest way to transmit gut bacteria is the faeco-oral route and parents could both be changing a baby셲 nappy, Liston says.

Children also pick up bacteria from their mother during birth and breastfeeding, and this may be passed to their father when he kisses his baby.

It is hard to know whether this immune convergence might be good or bad for your health, says O섵onnell. 쏧t could go either way depending on how they converge, she says.

Some changes might make a person more susceptible to infection, but they could also strengthen their defences against others. 쏻e don셳 really have a way to tell if someone has a 쁤ood immune system, says Maecker.

Journal reference: Nature Immunology, DOI: 10.1038/ni.3371
[The cellular composition of the human immune system is shaped by age and cohabitation]

Summary : Detailed population-level description of the human immune system has recently become achievable. We used a ‘systems-level’ approach to establish a resource of cellular immune profiles of 670 healthy individuals. We report a high level of interindividual variation, with low longitudinal variation, at the level of cellular subset composition of the immune system. Despite the profound effects of antigen exposure on individual antigen-specific clones, the cellular subset structure proved highly elastic, with transient vaccination-induced changes followed by a return to the individual’s unique baseline. Notably, the largest influence on immunological variation identified was cohabitation, with 50% less immunological variation between individuals who share an environment (as parents) than between people in the wider population. These results identify local environmental conditions as a key factor in shaping the human immune system.

Source and SeeMore : https://www.newscientist.com/article/2077496-your-immune-system-becomes-like-your-partners-when-you-cohabit/

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