Immunity and Ageing

In older individuals, numerous alterations in both innate and acquired immunity have been described and are collectively referred to as immunosenescence. Immunosenescence is a complex process characterized by multiple reorganizational and developmentally regulated changes, rather than a simple unidirectional decline of the entire immune function. Certain immunological parameters are consistently diminished in older individuals, and a reciprocal association exists between good immune function and overall health. While innate immunity tends to be relatively preserved in older individuals, acquired immunity is more susceptible to functional decline over time, as well as to the cumulative antigenic burden from a person immunobiography, the sum of antigens encountered throughout their lifetime. The reduction in the number of blood naïve cells, coupled with an increase in the frequency of memory cells, and the presence of inflamm-ageing are considered key hallmarks of immunosenescence. Longitudinal studies focusing on immune risk phenotypes have uncovered that the process of immunosenescence is highly context dependent. Comprehensive projects have contributed to identify the determinants of immune system variability, encompassing genetic and environmental factors, sex, smoking, and cohabitation. Consequently, age alone does not account for the entirety of immunosenescence. The diverse ageing experiences of individuals, shaped by their unique genetic makeup and life experiences, are even more pronounced in the context of the immune system.