A study conducted by Japanese researchers has revealed a significant rise in rare CD4 CTLs among exceptionally long-lived individuals. These specialized immune cells play a crucial role in coordinating the immune response and possess the unique ability to directly eliminate target cells, distinguishing them from typical CD4 T cells, which usually comprise less than 5% of the total T cell population. In 2019, this research team first highlighted the unusually high levels of CD4 CTLs found in supercentenarians. Their latest investigation delves into the timing of this increase and its progression with aging. The study involved blood samples from 28 participants aged between 70 and over 110. The median proportion of CD4 CTLs showed a steady increase across the age groups, rising from 4% in those aged 70-99 to 9.6% in the 100-109 age bracket, and reaching 17.6% among those aged 110 and older. This growth became particularly significant after the age of 100, although individual variability was notable. The researchers noted that the increase in these cells was not merely quantitative; specific clones expanded substantially, likely due to repeated encounters with persistent antigens. One prominent clone constituted an impressive average of 33.3% of the total CD4 CTLs, peaking at 53.8% in one centenarian. According to Kosuke Hashimoto, the lead author, "Instead of showing signs of fatigue, these cells remain highly active and could assist the body in managing ongoing threats that become more prevalent with age." Furthermore, the largest CD4 CTL clones exhibited receptor profiles similar to those found in T cells that proliferate in tumors, particularly in cases of lung, breast, and liver cancers. However, none of the participants over the age of 100 had a history of these cancers. The researchers tentatively propose that some of these cells might be capable of recognizing cancer-related targets before the disease manifests clinically. Additionally, the authors caution that while CD4 CTLs could enhance immune surveillance against cancer, their excessive proliferation has been linked to autoimmune and cardiovascular conditions, describing them as a "double-edged sword."
Informational material. 18+.
