Immune cells disrupt blood production with age
As we age, the composition of our blood changes. Certain white blood cells accumulate in increasing numbers, upsetting the balance. Researchers have now identified a concrete mechanism that explains why.
Age-associated myelopoiesis, the age-related shift in blood cell production, is well recognised but poorly understood. Older people produce proportionally more myeloid cells, a class of white blood cells, than younger people. This skewed balance is linked to higher risks of heart disease, infections and blood cancers.
Researchers publishing in Nature Aging describe new findings about a specific immune cell population: cytotoxic CD4+ T cells. Normally, CD4+ T cells help coordinate immune responses. With aging, a subgroup emerges that behaves more aggressively, resembling cells that typically attack infections directly. The researchers found that these cells accumulate in bone marrow and secrete a signalling molecule called CCL5.
CCL5 as the key link
CCL5 binds to the receptor CCR5 on blood stem cells. This signal drives stem cells to overproduce myeloid cells. The resulting imbalanced blood composition contributes to low-grade inflammation, which in turn amplifies aging processes: a well-known feedback loop in aging biology.
Notably, when researchers blocked CCR5 in aged mice, this effect was partly reversed. The mice showed signs of improved healthspan. That is a relevant finding because CCR5 inhibitors already exist as approved drugs, including for HIV treatment.
From mouse to human
Whether this mechanism operates in humans has not yet been demonstrated. Mouse aging models are useful but sometimes fall short, because aging in mice differs from aging in humans in important ways. CCR5 inhibitors also carry side effects. Nonetheless, this represents a concrete entry point for research into slowing age-related blood composition shifts.
From a longevity science perspective, it is notable that the immune system actively contributes to its own aging through a measurable signalling mechanism, making it, in principle, a target for intervention.
Search terms: age-associated myelopoiesis, CCL5-CCR5 immune aging, cytotoxic T cells bone marrow