Ever wondered what it looks like in your finger, say, when you get a splinter and your immune system leaps into action? Of course you have.
This amazing movie (double-click to play, I think) shows neutrophils (in green) responding to the presence of either a parasite (Leishmania major; in red) or to simple artificial beads (in blue), injected into the ear of a mouse. Neutrophils react to both foreign materials by galloping to the site and swarming the target. Neutrophils are a part of the rapid-response innate immune system, and this movie shows the first five hours of the response.
| 4-dimensional image series from the ear pinna of a LYS-eGFP mouse in which blue fluorescent beads and L. major had been deposited adjacent to one another in the skin of the same ear. eGFP-expressing cells are shown in green, L. major-RFP is shown in red, and beads are shown in blue. Playback speed is 1200x. Scale bar, 200?m |
From:
N. C. Peters, J. G. Egen, N. Secundino, A. Debrabant, N. Kimblin, S. Kamhawi, P. Lawyer, M. P. Fay, R. N. Germain, D. Sacks (2008). In Vivo Imaging Reveals an Essential Role for Neutrophils in Leishmaniasis Transmitted by Sand Flies Science, 321 (5891), 970-974 DOI: 10.1126/science.1159194
It’s been a while since I’ve taken immunology so this may be a “dumb” question, but what attracts the neutrophils to the artificial beads? Recognition of PAMPs driving a strong response to L. major makes sense to me, but how do the neutrophils recognize random matter as foreign? Do the neutrophils respond to KIRs?
It’s an excellent question. The neutrophils are not really attracted to the beads, but rather to the site of tissue damage from the needle that injected them — the beads are really a marker of the needle site. Similarly, the neutrophils were attracted to the sites of sandfly bites whether or not the bites injected in Leishmania. From the paper: ” … the initial inflammatory response to sand fly bite or needle-induced tissue damage drives the robust neutrophilic recruitment observed in these studies.”
What is it about tissue damage that attracts the neutrophils? There are several components released by damaged cells that act as innate immune triggers, including HMGB1 and uric acid (I’ve talked about both of them earlier). There may be other, as yet unidentified, factors, and I don’t think anyone has a solid idea of which is most important, or if it’s a combination.
[...] the Web: Read the paper online, Read a blog post on said paper (from science blog Mystery Rays from Outer Space). Watch this video of neutrophils (a type of white [...]
Woo! That’s bloody cool, isn’t it? Thanks.
But there’s no sound. I want to *hear* them.
But there’s no sound. I want to *hear* them.
So what are you imagining? I hear tiny hoofbeats, but I could also imagine yips and whoops, snarls and growls, or several other sound effects.
Hey, nice video. Was really interesting. It would be even better with sound though eh? ;)
[...] Comment on blog post and ask blog author question about how neutrophils are attracted to the beads. Get a response. Make my own blog post about the discovery. Reflect on the impact of the Web on science. [...]
[...] to this other movie I posted a while ago, which shows neutrophils in a mouse’s ear, being attracted to areas of [...]