This age-related deterioration affects both innate and adaptive immunity, compromising immune function and leading to chronic inflammation that accelerates aging. Immunosenescence is characterized by alterations in immune cell populations and impaired functionality, resulting in increased susceptibility to infections, diminished vaccine efficacy, and higher prevalence of age-related diseases. Chronic low-grade inflammation further exacerbates these issues, contributing to a decline in overall health and resilience. This review delves into the characteristics of immunosenescence and examines the various intrinsic and extrinsic factors contributing to immune aging and how the hallmarks of aging and cell fates can play a crucial role in this process. Additionally, it discusses the impact of sex, age, social determinants, and gut microbiota health on immune aging, illustrating the complex interplay of these factors in altering immune function. Furthermore, the concept of immune resilience is explored, focusing on the metrics for assessing immune health and identifying strategies to enhance immune function. These strategies include lifestyle interventions such as diet, regular physical activity, stress management, and the use of gerotherapeutics and other approaches. Understanding and mitigating the effects of immunosenescence are crucial for developing interventions that support robust immune responses in aged individuals.

The immune system plays a crucial role in protecting our bodies from harmful pathogens. It is divided into two segments: innate immunity and adaptive immunity. The innate immune system acts as an immediate but non-specific first responder to defend against pathogens, composed of phagocytic and natural killer cells. Besides innate immune cells, another important component of the innate system includes physical barriers like skin and mucous membranes. Meanwhile, adaptive immunity is more specialized and requires time to mount a high-affinity and specific response, relying on anticipatory receptors that recognize pathogen-specific antigens. The adaptive immune response is centered around B and T lymphocytes, which are produced in the bone marrow and thymus, respectively (Farber, 2020; Lam et al., 2024). With age, the ability of our immune system to mount productive and timely responses to pathogens diminishes.