Major New Function Discovered For the Spleen

circletimessquare writes "The spleen doesn't get much respect — as one researcher put it, 'the spleen lacks the gravitas of neighboring organs.' Those undergoing a splenectomy seem to be able to carry on without any consequences. However, some studies have suggested an enhanced risk of early death for those who have undergone splenectomies. Now researchers have discovered why: the spleen apparently serves as a vast reservoir for monocytes, the largest of the white blood cells, the wrecking crew of the immune system. After major trauma, such as a heart attack, the monocytes are disgorged into the blood stream and immediately get to work repairing the damage. '"The parallel in military terms is a standing army," said Matthias Nahrendorf, an author of the report. "You don't want to have to recruit an entire fighting force from the ground up every time you need it."'"

Re:HIV/AIDS

[Kligat]

AIDS is like a zombie virus, but for white blood cells, DoofusOfDeath. Unlike most viruses, it doesn't spread when the white blood cell explodes. The zombie white blood cell piles onto the healthy one and turns it into another of the infected. For more information, please direct the creators of Osmosis Jones [wikipedia.org] to create an R-rated sequel.

And in Related News..

[AtomicSnarl]

Lovely! This goes along with a recent discovery that the Appendix serves as reservoir for the gastrointestinal system's supply of friendly microbes which help digest our food.

No news yet on earlobes.

Re:Makes Sense

[Chris Burke]

You can lose a kidney, gall bladder, tonsils, etc. and they MUST have either had a use at one point or are meant for a very specific, yet seldom used task, i.e the Spleen being a repository for big white blood cells

Uh as pointed out kidneys have a rather important, crucial, and well-known use. The reason you can lose one is because the function the kidneys provide is so important that you evolved two so you have a backup.

The gall bladder does not provide a crucial function so it can be removed but this is not without consequence. Especially before your digestive system adjusts, you will have some quite noticeable side effects. Read: You don't want to be very far from a bathroom.

Tonsils are part of the lymphatic system. You can afford to lose them, but you are more likely to get upper respiratory infections.

These have all been known for a long time.

A better example of something thought to be useless which turned out not to be would be the appendix, which was thought to be a holdover from our purely herbivorous ancestors. But then recently they discovered it had another use -- as a reserve pocket of digestive bacteria that can be used to "reboot" the digestive system if something wipes out the microbes in the intestines.

Re:How could the miss that?

[Inda]

Yeah but they're talking about blood cells here. I've had my white cells counted under a microscope, so I know it can be done.

Re:Makes Sense

[Fallen Kell]

You can lose "a" kidney because you have 2. If you lose both, you are dead... We have two because without one we are dead, and they are in a fairly unprotected part of the human body, so our ancestors/predictors who developed two tended to survive to procreate better then the ones without two.

The tonsils are part of the lymphatic system and also help our immune system (like the spleen) mainly by being the mechanism where the ducts for our immune system to access the upper repritory system (i.e. mouth, throat). You can "live" without tosils, but you are more prone to respritory infections, which is manageable in this post-penicillin medical world.

The gall bladder is actually something that is very important to the digestive system. It isn't a "vital" organ (again, meaning you can live without it), but fatty foods will possibly not be handled properly by the body. The gall bladder stores up and concentrates the bile (produced in your kidneys) and regulates when to release it into the digestive tract properly. Without the gall bladder, the kidneys are directly releasing the gall into the tract whenever the kidney produces it. The trigger to produce bile is fat in the blood stream, which happens by absorption in the digestive tract as well as from other sources as well. One possible major drawback to not having a gall bladder is that you might be running to the closest bathroom almost immediately after eating a meal which contained lots of fats because your kidney just dumped a ton of bile into your digestive tract and you have automatic diarrhea from that much gall.

Re:How could the miss that?

[kheldan]

In the grand view of things, medical science is still in it's infancy, even if it's late infancy; there are still more things that are NOT understood than that ARE understood. From my layman's perspective it seems to me like trying to work on an automobile's engine while it's running, but unlike that engine, if you shut down and dismantle the human engine, you can't just put it back together again, pour gas and oil in it, and expect it to run ever again. It seems that since we have developed better and better imaging technologies this situation has begun to improve, but I think it'll take even bigger leaps in that technology before we can really start getting a handle on "the basics".

Liar!

[Anonymous Coward]

Since when do medical students get any time at all for sleep?

Re:How could the miss that?

[BigDukeSix]

The important discovery here is not that the spleen has monocytes in it, because you do in fact see a ton of them when you look at splenic tissue under the microscope. The interesting thing about this discovery is that the spleen can (evidently) release a bunch of those cells in response to an injury. The bone marrow does this too, but the WBCs it releases are immature, and we know that there are changes in the way WBCs function as they age. It would appear that "spleen" WBCs are optimized for their tissue repair properties, while "bone marrow" WBCs are better for fighting infection.

It will be interesting to see if this holds true in humans. Lots of animals have spleens that seem more functional than ours. Cats and dogs, for example, can "transfuse" themselves with the blood from their spleen in response to bleeding, but this does not hold true for humans.

Re:How could the miss that?

[interkin3tic]

I'm sure someone cut open a spleen before and looked at it through a microscope. Wouldn't you see an unusually high concentration of the monocytes?

For one thing, compared to what? As the article points out

Its such a vascularized organ, and the risk of big-time hemorrhaging is so great, that if the spleen ruptures, itâ(TM)s a surgical emergency,â said James N. George, a hematologist with the University of Oklahoma Health Sciences Center.

It's full of blood, if you thought you noticed a high amount of monocytes, you'd probably think: they're blood cells and the spleen is full of blood cells. The finding is, as I understand it, that BLOOD from the spleen is higher in monocytes. You'd have to compare blood from the spleen to blood circulating in other organs.

The other issue is that monocytes would be hard to specifically identify, and probably impossible to count in tissue slices. This page [profelis.org] has some examples of what monocytes look like when they're specifically stained (with hematoxylin and eosin I think), and what other blood cells look like. That's when they're stained just right and drawn out of an organ. If you're looking at slices of a spleen under a microscope, that's not going to jump out at you even if you were staining with H&E. The article used antibodies to specifically identify only monocytes. Antibodies recognize and can label specific proteins, they chose proteins that would be specific to monocytes. That's not something you do unless you're looking for monocytes specifically.

So you wouldn't notice monocytes unless you stained with antibodies specific to them, and even then, you wouldn't be able to compare them accurately in microscope sections.

  In the real article [sciencemag.org], the authors seem to have used fluorescence-activated cell sorting (FACS) [wikipedia.org] on spleen isolated blood to compare to circulating blood from other organs.

FACS as I understand it (never done it myself, only heard about, and I'm not reading the real article too closely either) is where isolated cells one at a time are sprayed through a laser. If the cell has a fluroescent tag on it, that makes it deviate from the path it would take if it doesn't. You can collect cells that deviate and cells that don't, the machine counts them, and you can then compare the ratios (easier than counting in a microscope.) So they were able to use that to show it had a higher ratio.

Collecting blood from isolated tissues, prepping it with the antibodies for monocytes, prepping that for FACS and then actually doing FACS is not trivial, you're not going to be doing it unless you're specifically testing a hypothesis like the ones the authors had.

(disclaimer: I'm not an expert in spleens, immunology, or FACS and I didn't read either article in depth.)

Re:How could the miss that?

[juancnuno]

30% of a horse's red blood cells are stored in its spleen, for release when needed. Like for extra blood oxygen capacity under strenuous exercise. See http://en.wikipedia.org/wiki/Spleen [wikipedia.org] See also http://en.wikipedia.org/wiki/Blood_doping [wikipedia.org]

what you said is fine and good

[circletimessquare]

but you meant to say "liver" instead of "kidney" everywhere in the third paragraph. the liver creates bile that empties into the gallbladder, not the kidneys

Re:New? Again?

[mollusc]

You've completely missed the point of the article. It isn't some general statement about monocytes being important, or the spleen having monocytes in it.

Instead, it shows a) that there are far more monocytes in the spleen than in the circulation (novel), b) where in the spleen they hang out, using excellent microscopy (novel) and c) how they are released very rapidly in response to injury (also novel).
This ain't in your local newsweekly, either, this is in Science, and you don't get a research article in Science unless what you've got is both novel information and beautiful work.

Here's the abstract:
A current paradigm states that monocytes circulate freely and patrol blood vessels but differentiate irreversibly into dendritic cells (DCs) or macrophages upon tissue entry. Here we show that bona fide undifferentiated monocytes reside in the spleen and outnumber their equivalents in circulation. The reservoir monocytes assemble in clusters in the cords of the subcapsular red pulp and are distinct from macrophages and DCs. In response to ischemic myocardial injury, splenic monocytes increase their motility, exit the spleen en masse, accumulate in injured tissue, and participate in wound healing. These observations uncover a role for the spleen as a site for storage and rapid deployment of monocytes and identify splenic monocytes as a resource that the body exploits to regulate inflammation.