International Journal of Molecular Zoology 2024, Vol.14, No.4, 197-210 http://animalscipublisher.com/index.php/ijmz 200 3 Immune Function and Longevity 3.1 The link between immune function and lifespan The relationship between immune function and lifespan is complex and multifaceted. Immunosenescence, the gradual deterioration of the immune system with age, plays a significant role in this dynamic. This process affects both innate and adaptive immunity, leading to increased susceptibility to infections, cancer, and autoimmune diseases in older individuals (Salminen, 2021). Interestingly, some studies suggest that immunosenescence may also have adaptive aspects, potentially contributing to longevity by triggering anti-inflammatory responses that counteract age-related pro-inflammatory environments (Santoro et al., 2021). This dual role of immunosenescence highlights the intricate balance between immune function and lifespan. 3.2 Mechanisms of immune-mediated longevity 3.2.1 Immunosenescence and its impact on aging Immunosenescence is characterized by a decline in immune cell function, including reduced antibody responses and a decrease in the number of naive immune cells (Rodríguez et al., 2021). This decline is more pronounced in adaptive immunity compared to innate immunity. The accumulation of senescent immune cells and the associated chronic low-grade inflammation, termed "inflammaging," are hallmarks of this process. These changes contribute to the increased prevalence of age-related diseases and a general decline in health in the elderly. 3.2.2 Role of inflammation in aging Inflammaging, the chronic, sterile inflammation associated with aging, is a significant factor in the aging process. It results from the accumulation of pro-inflammatory factors and the decline in the immune system's ability to regulate inflammation. This persistent inflammation can lead to tissue damage and the development of various age-related diseases, including cardiovascular diseases, neurodegenerative disorders, and cancers (Fulop et al., 2018). However, some researchers argue that inflammaging may also have adaptive benefits, such as promoting anti-inflammatory responses that help maintain homeostasis and support longevity. 3.3 Comparative studies of longevity in different vertebrate species Comparative studies across different vertebrate species provide valuable insights into the relationship between immune function and longevity. For instance, research on wild animals has shown that immunosenescence is not unique to humans but is also observed in other species, including mammals, birds, and reptiles. These studies reveal that, similar to humans, age-related declines in immune function are more evident in adaptive immunity and are associated with increased inflammatory markers (Peters et al., 2019). In long-lived species like the painted turtle (Chrysemys picta), evidence suggests that immunosenescence may not be as pronounced, and older individuals can maintain robust immune functions (Figure 2) (Judson et al., 2020). This finding contrasts with the typical pattern observed in mammals and highlights the variability in immune aging across species. Additionally, studies on Drosophila melanogaster have shown that evolutionary changes in immune function, particularly in the Toll pathway, can contribute to increased longevity and improved resistance to infections (Fabian et al., 2018). These comparative studies underscore the importance of immune function in determining lifespan and highlight the diverse strategies employed by different species to achieve longevity. The study of Judson et al. (2020) illustrates a positive correlation between age and natural antibody titers in painted turtles, with older individuals exhibiting higher antibody levels than younger ones. This trend is consistent across both sexes and juveniles, indicating that immune function, as measured by natural antibodies, may enhance with age in this species. The equation and R² value suggest a modest yet significant relationship, emphasizing that age is a predictor of immune capability in painted turtles. The age scale bars highlight the distribution of ages among the studied groups, providing context for the observed correlation. 4 Immune Function and Adaptation 4.1 The Role of immune function in environmental adaptation Immune function plays a critical role in the adaptation of vertebrates to diverse environmental conditions. The ability to mount an effective immune response is essential for survival in hostile environments, as it ensures
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