The immune systems of people who live past 110 hold a surprise that could help explain their extraordinary longevity.
Researchers studied certain immune cells in centenarians and supercentenarians, meaning people aged at least 110. They focused on T lymphocytes, cells that help monitor the body. One particular population becomes much more prevalent around the age of 100.
A T lymphocyte observed under a scanning electron microscope and colorized.
Credit: NIAID — CC BY 2.0
These cells are CD4 T lymphocytes capable of directly killing certain cells. CD4 lymphocytes are usually known mainly for coordinating the immune response. Here, some of them acquire destructive abilities. The researchers call them cytotoxic CD4 T lymphocytes.
To understand what makes them different, the team examined the cells one by one and compared how they functioned. It found that certain families of lymphocytes had multiplied extensively. Cells from the same family share a common origin and recognize the same target. This multiplication indicates that they had probably encountered that target repeatedly.
The phenomenon does not resemble an immune system that becomes exhausted with age. The cells observed retained signs of activity. Their abundance increased mainly from around the age of 100, indicating a gradual transformation of the immune response in people reaching very advanced ages.
Another result draws attention. Some sequences that enable these cells to recognize their target resembled those of lymphocytes previously observed in tumors, particularly lung cancers. These cells may therefore be capable of recognizing, or even destroying, tumors.
People who reach the age of 110 are an extremely rare population. Their bodies may exhibit several characteristics linked to genetics, lifestyle, or medical history. Distinguishing what actually promotes longevity from what is simply a consequence requires further research.
Researchers can now investigate which targets trigger the multiplication of these cells over the decades. They can also determine whether the cells actually eliminate cancer cells or other cells that have become abnormal with age. This step will help establish whether this immune response directly contributes to healthy aging.