A mysterious organ that’s most active in childhood might play a previously underappreciated role in adults.
In a study of almost 2,300 adults who underwent chest surgery, removing the thymus gland was associated with higher rates of death and of cancer within the next few years, researchers report in the Aug. 3 New England Journal of Medicine. The discovery pushes back on a long-held belief that the immune system organ is somewhat expendable in adulthood.
“This is a really important finding,” says immunologist Dong-Ming Su of the University of North Texas Health Science Center at Fort Worth, who was not involved in the work. Prior to this study, he says, “there was no direct evidence to demonstrate [the thymus’] importance in adults.”
The thymus resides in the chest between the lungs, right in front of and above the heart. In infants, the gland almost completely covers the heart. It pumps out immune cells called T cells, which detect foreign invaders that could cause illness.
But the gland’s activity dwindles after puberty, producing fewer new T cells as we age. Adults mostly rely on memory T cells, long-lived cells that rapidly produce specialized T cells in response to intruders the body has fought before. The thymus gradually wastes away and gets replaced by fat.
“It progressively becomes something that looks like more of a fatty blob,” says hematologist-oncologist David Scadden of Massachusetts General Hospital in Boston. Doctors might excise an adult’s thymus if it contains an abnormal growth, to help alleviate an autoimmune disease or simply because it’s in the way during chest surgery, he says. “It’s often removed because it’s not thought to be very consequential.”
To look at consequences of getting rid of the gland, Scadden and colleagues examined health outcomes in 1,146 patients who had their thymus removed from 1993 to early 2020 at Mass General. The researchers compared those patients’ outcomes with…
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