Biology textbooks are blunt--neutrophils are mindless killers. These white blood cells patrol the body and guard against infection by bacteria and fungi, identifying and destroying any invaders that cross their path.
But new evidence, which may lead to better drugs to fight deadly pathogens, indicates that neutrophils might actually distinguish among their targets.
A scientist in the lab of Whitehead Member Gerald Fink has discovered that neutrophils recognize and respond to a specific form of sugar called beta-1,6-glucan on the surface of fungi. This sugar comprises just a small fraction of the fungal cell wall, much less than another sugar with a slightly different chemical conformation called beta-1,3-glucan. Because the scarce form of the sugar elicits a much stronger reaction from immune cells than the abundant one, it appears that neutrophils can distinguish between two nearly identical chemicals.
"These results show that engulfment and killing by neutrophils varies, depending on cell wall properties of the microbe," explains Whitehead postdoctoral researcher Ifat Rubin-Bejerano, first author on the paper, which appears July 11 in the journal Cell Host & Microbe. "We showed that neutrophils respond in a completely different way to slight changes in sugar composition. If we are able to use this unique sugar to excite the immune system, it may help the human body fight infection."
"Previously, everyone thought that these key cells of the immune system weren't picky and would eat anything that looked foreign," adds Fink, who is also an MIT professor of biology. "Ifat's work has shown that the cells aren't little Pac-Men, but can discriminate one pathogen from another."
Rubin-Bejerano had evidence that neutrophils respond to beta-glucan. After coating tiny beads with a variety of substances (including beta-1,3-glucan and beta-1,6-glucan), she exposed them to the neutrophils and was surprised to see a striking difference in their response to the two sugars. The neutrophils quickly engulfed many of the beads coated with beta-1,6-glucan, but only a few of those covered in beta-1,3-glucan.
Previous studies indicated that blood serum (basically blood minus cells) helps neutrophils recognize their enemies, so Rubin-Bejerano decided to look for clues to their response in this mixture. She identified several proteins in serum that bind to beta-1,6-glucan, but not beta-1,3-glucan, and then pinpointed a molecule on the surface of the neutrophil that recognizes these proteins.
To link her experiments back to real fungi, Rubin-Bejerano worked with the pathogen Candida albicans, which is the most common fungus in blood stream infections. She used an enzyme to digest beta-1,6-glucan from the fungal cell wall, leaving the beta-1,3-glucan intact. She then unleashed the neutrophils on these altered cells and observed a 50 percent reduction in the immune response.
Our bodies maintain a fine balance between the immune system and microbes. Antibiotics and antifungals tilt the balance in favor of the immune system by targeting the microbes directly. A substance like beta-1,6-glucan could help tilt this balance further by stimulating immune cells.
Rubin-Bejerano's work offers hope for combating the growing problem of microbial infections, which can seriously threaten human health--particularly in patients with compromised immune systems. In fact, Rubin-Bejerano co-founded a company called ImmuneXcite to explore this possibility.
Source: Whitehead Institute for Biomedical Research
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8 comments:
I love these biology posts of yours the best - wanted to be a doctor myself but sucked at chemistry...so dropped it in my 'O' levels
Hi Random,
you would have made a great healer
I bet the energy running through your hands could raise the dead if you put your mind to it.
We spend too much time defeating ourselves with what we cannot do, instead of pursuing what we CAN.
I'm rather picky about sugar too. I don't like it in my system.
Alas Aggie, I live off sugar
though no doubt I'll pay the price for my sweet tooth.
Modern medicine recognises that we are in fact each individual, in more senses than one, and no one remedy works for all ...
what is good for one is poison for another is true I'm told since man his immortality for a moment sold
Well, if it makes you a sweetie, that's ok then!
I was mentioned to your blog by Mystic Rose and I found many of your posts very interesting and beneficial for my brain. I'm one who really likes sugar btw, I love it to death, if I don't drink at least two to three sodas during the day I don't feel well because my body has no sugar to run off of. Which kind of makes me think if I'm a diabetic because it runs in my family. But I never knew most of this information about sugar, it's very interesting.
But your blog is very educational and I can't stop reading your posts, anyway I went back to your post you posted back in April entitled Neural Paths.
So we actually do use more than 10% of our brains, I just have a quick question and I know it is possible but I'm trying to think of how to describe this but is it possible to use even more than that, what I mean is well.... okay just think of this. I'm a person who always reads information but sometimes I'll forget what I read while at the same time I don't forget and I will sometimes end up memorizing everything I just read because I crave it and yet I feel like my mind is not expanding yet it is. Am I still using only 20% or is it possible that the mind is actually using more than that as I hold on to more information or is this just a question that I'm asking and searching for that can't be answered?
I just created another blog called Just A Thought, I only have one post in there right now but read the post I just posted in there about where a thought originates from in our mind and give it some thinking, I'm always looking for advice about these topics, which truthfully I just found here.
I also have my original blog which you can go to both in my profile. I post and write whatever in there but I try to keep it about nature which is what I originally created it for.
But I really love your blog and I will definitely be back to read more of your information.
Later and take care. :)
Hi Aggie, I can be as sweet and endearing as you like me to be.
But never tooo sweet or sickly!
Hi Mavin,
we've got an interesting series on tv at the moment called "My beautiful Brain" exploring how brains (and memory) are developed.
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