Longevity is not merely the privilege of adding years to one’s life. It is, above all, the ability to add life to those years by preserving the body’s functionality and the mind’s clarity. Supercentenarians—people who live beyond the age of 110—constitute an exceptionally rare natural experiment. They have not simply survived longer; they have managed to postpone or avoid diseases that commonly accompany aging, such as cancer, cardiovascular disease, and neurodegenerative disorders.
What protects these people? Genes undoubtedly play a role, as do diet, physical activity, psychological resilience, and the social environment. A new study (Hashimoto et al. Cell Reports 2026), however, draws attention to another mechanism: a small but remarkably effective group of immune cells known as CD4 cytotoxic T lymphocytes, or CD4 CTLs.
Under normal circumstances, CD4 T lymphocytes function primarily as the “coordinators” of the immune response. They activate and guide other cells without usually killing the targets themselves. CD4 CTLs are an unusual exception: they retain their coordinating identity while simultaneously acquiring cytotoxic properties. They produce perforin and granzymes, substances through which they can destroy virus-infected cells, senescent cells, and possibly early cancer cells.
The researchers studied blood samples from 28 individuals divided into three age groups: 70–99, 100–109, and 110 years and older. The proportion of CD4 CTLs increased strikingly with age. They accounted for a median of 4% of T lymphocytes in the first group, 9.6% among centenarians, and 17.6% among supercentenarians. It appears, therefore, that around the age of 100, a remarkable reorganization of the immune system takes place.
The most important finding is that these cells did not display the typical signs of immune exhaustion. Despite the exceptionally advanced age of the individuals from whom they were obtained, they retained their functionality and flexibility. The immune system of supercentenarians did not resemble merely a weakened army whose remaining soldiers were still standing at the ramparts. It had readapted to emerging threats and selected specific, experienced units capable of recognizing and neutralizing persistent dangers.
Indeed, the CD4 CTLs showed extensive clonal expansion. This means that certain cells, after presumably recognizing a specific target, multiplied to create numerous copies of themselves. The dominant clone accounted, on average, for one-third of these cells, while in one centenarian it represented almost 54%. This picture suggests repeated encounters with persistent antigens and the presence of an immune memory that continues to learn even at an extremely advanced age.
Even more intriguing was the observation that receptors belonging to some of these clones resembled receptors found on T lymphocytes from patients with lung, breast, or liver cancer. The supercentenarians in the study did not have these cancers. It is therefore possible—although this has not yet been demonstrated—that their immune systems had recognized and eliminated cells carrying early malignant changes before a clinically detectable cancer could develop.
As we grow older, mutations, dysfunctional mitochondria, and senescent cells gradually accumulate. Senescent cells are not inert. They secrete inflammatory substances, disrupt neighboring tissues, and sustain a chronic state of low-grade inflammation known as “inflammaging.” If a specialized population of cytotoxic CD4 cells can remove part of this biological burden, it may contribute substantially to the preservation of homeostasis.
Aging, therefore, is not merely a linear progression of deterioration. It is a continuous contest between damage and repair, disorganization and adaptation. Through allostasis, the organism seeks to maintain stability in the midst of change. When this effort becomes prolonged or fails, allostatic load accumulates becomes injurious and after a certain point cacostasis becomes established. Supercentenarians appear to possess the capacity to transform part of this chronic challenge into an effective adaptive response, thereby avoiding destructive and lethal dysregulation for many decades.
Scientific caution is nevertheless essential. The study was small, examined cells circulating in the blood, and does not prove that CD4 CTLs cause longevity or prevent cancer. They may be a cause, a consequence, or simply an accompanying feature of healthy aging. These cells must also be studied within human tissues, and the precise targets they recognize need to be identified. The message, however, remains optimistic.
The immune system does not merely grow old; it evolves, selects, and adapts. The medicine of longevity may one day seek not simply to slow deterioration, but to strengthen this intrinsic capacity of the organism to recognize, remember, and protect itself. Supercentenarians do not show us how to defeat time. They show us how the human organism can continue to engage in a creative dialogue with it.
George P. Chrousos, MD, MACP, MACE, FRCP, ΣΞ, Professor of Pediatrics and Endocrinology Emeritus, Holder, UNESCO Chair on Adolescent Health Care, Director, University Research Institute of Maternal and Child Health and Precision Medicine, Medical School, National and Kapodistrian University of Athens.
Supercentenarians and the Vigilant Guardians of the Immune System
Longevity is not merely the privilege of adding years to one’s life. It is, above all, the ability to add life to those years by preserving the body’s functionality and the mind’s clarity. Supercentenarians—people who live beyond the age of 110—constitute an exceptionally rare natural experiment. They have not simply survived longer; they have managed to postpone or avoid diseases that commonly accompany aging, such as cancer, cardiovascular disease, and neurodegenerative disorders.
What protects these people? Genes undoubtedly play a role, as do diet, physical activity, psychological resilience, and the social environment. A new study (Hashimoto et al. Cell Reports 2026), however, draws attention to another mechanism: a small but remarkably effective group of immune cells known as CD4 cytotoxic T lymphocytes, or CD4 CTLs.
Under normal circumstances, CD4 T lymphocytes function primarily as the “coordinators” of the immune response. They activate and guide other cells without usually killing the targets themselves. CD4 CTLs are an unusual exception: they retain their coordinating identity while simultaneously acquiring cytotoxic properties. They produce perforin and granzymes, substances through which they can destroy virus-infected cells, senescent cells, and possibly early cancer cells.
The researchers studied blood samples from 28 individuals divided into three age groups: 70–99, 100–109, and 110 years and older. The proportion of CD4 CTLs increased strikingly with age. They accounted for a median of 4% of T lymphocytes in the first group, 9.6% among centenarians, and 17.6% among supercentenarians. It appears, therefore, that around the age of 100, a remarkable reorganization of the immune system takes place.
The most important finding is that these cells did not display the typical signs of immune exhaustion. Despite the exceptionally advanced age of the individuals from whom they were obtained, they retained their functionality and flexibility. The immune system of supercentenarians did not resemble merely a weakened army whose remaining soldiers were still standing at the ramparts. It had readapted to emerging threats and selected specific, experienced units capable of recognizing and neutralizing persistent dangers.
Indeed, the CD4 CTLs showed extensive clonal expansion. This means that certain cells, after presumably recognizing a specific target, multiplied to create numerous copies of themselves. The dominant clone accounted, on average, for one-third of these cells, while in one centenarian it represented almost 54%. This picture suggests repeated encounters with persistent antigens and the presence of an immune memory that continues to learn even at an extremely advanced age.
Even more intriguing was the observation that receptors belonging to some of these clones resembled receptors found on T lymphocytes from patients with lung, breast, or liver cancer. The supercentenarians in the study did not have these cancers. It is therefore possible—although this has not yet been demonstrated—that their immune systems had recognized and eliminated cells carrying early malignant changes before a clinically detectable cancer could develop.
As we grow older, mutations, dysfunctional mitochondria, and senescent cells gradually accumulate. Senescent cells are not inert. They secrete inflammatory substances, disrupt neighboring tissues, and sustain a chronic state of low-grade inflammation known as “inflammaging.” If a specialized population of cytotoxic CD4 cells can remove part of this biological burden, it may contribute substantially to the preservation of homeostasis.
Aging, therefore, is not merely a linear progression of deterioration. It is a continuous contest between damage and repair, disorganization and adaptation. Through allostasis, the organism seeks to maintain stability in the midst of change. When this effort becomes prolonged or fails, allostatic load accumulates becomes injurious and after a certain point cacostasis becomes established. Supercentenarians appear to possess the capacity to transform part of this chronic challenge into an effective adaptive response, thereby avoiding destructive and lethal dysregulation for many decades.
Scientific caution is nevertheless essential. The study was small, examined cells circulating in the blood, and does not prove that CD4 CTLs cause longevity or prevent cancer. They may be a cause, a consequence, or simply an accompanying feature of healthy aging. These cells must also be studied within human tissues, and the precise targets they recognize need to be identified. The message, however, remains optimistic.
The immune system does not merely grow old; it evolves, selects, and adapts. The medicine of longevity may one day seek not simply to slow deterioration, but to strengthen this intrinsic capacity of the organism to recognize, remember, and protect itself. Supercentenarians do not show us how to defeat time. They show us how the human organism can continue to engage in a creative dialogue with it.
Commentary
On CD4 CTLs in supercentenarians: Signs of adaptive expansion in healthy aging, by Kosuke Hashimoto et al., Cell Reports, August 19, 2026 Open access; DOI: https://www.cell.com/cell-reports/fulltext/S2211-1247(26)00806-5
Author’s Affiliation
George P. Chrousos, MD, MACP, MACE, FRCP, ΣΞ, Professor of Pediatrics and Endocrinology Emeritus, Holder, UNESCO Chair on Adolescent Health Care, Director, University Research Institute of Maternal and Child Health and Precision Medicine, Medical School, National and Kapodistrian University of Athens.
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