Fig. 3

Age-related alterations affect both the adaptive and innate immune systems. In the adaptive immune system, there is a decline in the population of naive CD4⁺ T cells, CD8⁺ T cells, Treg cells, and B cells, whereas memory cells become more prevalent. In the innate immune system, the functionality of monocytes/macrophages is compromised, and neutrophils exhibit reduced capabilities in terms of NET formation, phagocytosis, and chemotaxis, along with an increased susceptibility to apoptosis. Furthermore, there is an increase in CD56^dim NK cells and a decrease in CD56^bright NK cells. The population of dendritic cells also decreases, and their anti-phagocytic abilities weaken with age