Galen considered the spleen to be a source of one of the four bodily humors, specifically the black bile associated with irritable, melancholic cranks. “Splenetic” describes a person affected by ill humor or irritability, although the first book of the Talmud (Berakoth 61) says the spleen “produces laughter” (and “the lungs absorb all kinds of liquids”, and “the liver is the seat of anger”).
The new research entitled “Identification of Splenic Reservoir Monocytes and Their Deployment to Inflammatory Sites” and published at Science Mag shows that the spleen is a reservoir for monocytes, and that in the event of a serious trauma to the body like a heart attack, gashing wound or microbial invasion, the spleen will disgorge those monocyte into the bloodstream.
From 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.
The role of spleen in the production of antigens is well known. It has been found that the brain has the capacity to stimulate the production of antigen specific antibodies by its parasympathetic autonomic output.
But spleens are rather sensitive organs and can rupture during contact sports or accidents, at which point the risk of hemorrhaging is so that a surgical removal is the best choice. The new findings doesn’t counter this practice, but suggest that the loss of the organ is more than a mere “inconvenience”, and could help explain previous reports showing an enhanced risk of early death among people who have undergone splenectomies. In 1977 researchers compared a group of WW2 veterans who had had their spleens removed as a result of battle injuries with a similar size sample of veterans who had suffered other war injuries but had kept their spleens. The splenectomized men, the researchers found, were twice as likely to die of cardiovascular disease as were the veterans in the control group.