Bacteria, biology, Complement system, Health, Immune system, microbes, microbiome, Mouse, Popular science, science
The skin is one of our body’s first lines of defense, but it’s also home to a rich community of microbes — the skin microbiome. These bacteria are important in protecting us from pathogens; changes in the skin microbiome are linked with conditions ranging from dermatitis to psoriasis. In a paper published this month in the journal PNAS, a team of scientists from the University of Pennsylvania showed that these bacteria don’t just live on our skin, but also play a role in regulating our immune response.
The researchers took samples from the skin of laboratory mice and used modern sequencing technology to figure out how many kinds of bacteria were living there and how similar they were to one another. To investigate how the immune system affects the skin microbiome, they then treated some mice with a chemical that blocks a component of the complement system, which is part of the innate immune system, and checked how the bacterial community changed. Although both groups had roughly the same amount of bacteria on their skin, there were fewer different kinds of bacteria on the skin of the complement-blocked mice. In other words, they had a significantly less diverse skin microbiome than the untreated mice. The researchers also found that these mice had lower levels of various genes related to immunity and fewer immune cells in their skin.
The team decided to find out if this interaction was two-way — that is, whether the skin microbiome can affect the immune system instead of just being regulated by it. To do this, they started with germ-free mice — mice without any bacteria on their skin — and infected them with a skin microbiome. Examining genes related to the complement system, the researchers found that many of them became significantly more active after the mice gained skin bacteria.
I don’t think this study presents any evidence that the bacteria are actively or directly regulating the immune response; it’s also possible that the changes are because the complement system is responding to the presence of bacteria on the skin. It would be cool if the bacteria were active players, but either way it’s clear that our skin bacteria plays a role in coordinating some of our earliest lines of defense.
Chehoud C, Rafail S, Tyldsley AS, Seykora JT, Lambris JD, & Grice EA (2013). Complement modulates the cutaneous microbiome and inflammatory milieu. Proceedings of the National Academy of Sciences of the United States of America, 110 (37), 15061-6 PMID: 23980152
Matt Russell said:
Reblogged this on Small Organisms Big Benefits and commented:
A must read for everyone interested in the benefits of bacteria.
Well, it makes sense, doesn’t it? Our skin is the largest organ of our body. It would be reasonable to assume that anything that interacts with our skin, would influence just about all our other systems (not just the immune system) – for good or bad.
I guess the big question is: does having a plentiful, diverse bacterial population in the skin microbiome lead to a healthier person? If so, then kids everywhere will rejoice – no more baths! 😉
Yeah, it seems pretty sensible after the fact. The hard part is thinking of it first and showing that it’s true. 😉
From what I understood, a rich skin microbiome does contribute to being healthier. It probably wouldn’t be good to start foregoing baths, but I think it’s possible to be too clean — have a look at the hygiene hypothesis.
The Science Table said:
Reblogged this on Escynce.
What was the chemical they used to block complement? How specific is it? Can’t get through the paywall 😦 . Very interesting though!
The chemical, which they describe as “specific and potent C5aR [complement C5a receptor] antagonist”, is “the cyclic hexapeptide Ac-F[OP(D)Cha-WR] (acetylated
phenylalanine–[ornithine-proline(D)cyclohexylalanine-tryptophan-arginine])”. To be honest, that doesn’t mean anything to me, but a Google search for Ac-F[OP(D)Cha-WR] brings up lots of hits about inhibiting complement.
Very very cool. Below is a 2010 paper also using this inhibitor. I guess some bugs use activation of C5a as a mechanism of immune evasion. Add that to the growing list of things I didn’t know. Killing/anergizing T, B, Mac or Dendritic cells I am used to, but using complement against us? Very cool.
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