Immunosenescence is a concept focused on the alterations in the aged immune system. Aged immune cells may be dysfunctional and inactive or hyper-inflammatory. Adaptive immunity shows increases in TNFα+ plasma cells producing autoantibodies and inflammatory, aged B cells (ABCs) that are unresponsive through their B cell receptor. Antigen-specific antibody production, one carbon metabolism and oxidative phosphorylation are decreased with age. There is an increased frequency of IL10+ regulatory T follicular helper cells that fail to interact with B cells effectively, ultimately results in reduced T cell priming. T cells also show impaired metabolism, reduced SIRT1, but increased senescent features. Innate Immunity shows increases in myelopoiesis, elevated basal NLRP3 activation, decreased phagocytosis and reduced NAD metabolism. Other innate cells, including natural killer cells, eosinophils and neutrophils are altered in number and function.