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."'"

Comments

How could the miss that?

[13bPower]

How could they miss that? 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?

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 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, the authors seem to have used fluorescence-activated cell sorting (FACS) 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.)

No problem.

[T Murphy]

However, some studies have suggested an enhanced risk of early death for those who have undergone splenectomies

I don't see how this is a problem. This is a new discovery- those old spleens didn't have this functionality yet.

Splenectomy Patients

[sp1nl0ck]

My Dad had his spleen removed when he was a kid, and a number of years ago (10) was told he had to carry a card around with him that said something like

"I have had my spleen removed and may be subject to overwhelming infection."

Seriously. We told him he shouldn't use that as his opening gambit when talking to girls :-)

Re:And in Related News..

[The_mad_linguist]

Earlobes serve as a reservoir for gems and precious metals, in case of emergency financial distress.

IAAMS

[xanthines-R-yummy]

I Am A Medical Student...

You need all of the things you listed to live a normal life. Sure, you can SURVIVE without those organs but medicine/science have known for quite awhile now that losing your spleen makes you vulnerable to infections, which is why you typically get vaccines galore before removing it (vaccines aren't a replacement for spleens, btw; it's better than nothing!). I think anyone's who's had their gall bladder removed will tell you they wish they had a functioning one. It helps make your stool a lot more pleasant! While you can live quite awhile with only one kidney, there's evidence out there that kidney donors may have shortened lifespans. Your tonsils are lymph nodes which house immune cells.

By your reasoning, it doesn't appear we need 5 fingers on each hand. We can surely survive with 4, 3, or even none. For that matter, might as well get rid of that pesky arm!

There's a difference between being necessary for life, and being really really REALLY useful.

/I kind of forgot what I was typing about.
//Going to bed...
///I dream of slashies

Not so much contamination; water & salt retent

[interactive_civilian]

I think that is "neat" and also makes me curious on how contaminated things like our blood and urine must have been to require 2 kidneys and other "non-essential" organs

Remember that kidneys aren't only for filtering waste, their other primary functions are salt and bicarbonate recovery, pH balance (getting rid of excess H+ ions using phosphates and NH3 from the glutamine -> glutamate reaction), and water recovery. In fact, with the elongated Loop of Henle, one could argue that water retention in arid environments is one of the primary functions of the human kidney. They are very good at concentrating and getting rid of nitrogenous wastes while retaining important water, salts, and bicarbonate. This is probably a product of evolving in Eastern Africa. ;)

Point being, having two kidneys is probably less due to toxicity of blood and more due to efficient water and salt recovery as organisms moved from aquatic to terrestrial environments. Just sayin'. :)