Loss of Renal Function Causes Premature Aging of the Immune System

<b><i>Background:</i></b> Uremia-associated immune deficiency is a well-known complication of loss of renal function and contributes significantly to the overall mortality and morbidity of patients with end-stage renal disease. Chronic inflammation and increased oxidative stress are underlying the uremia-associated immune deficiency. <b><i>Summary:</i></b> In this review, the differential impact of uremia on the cellular immune system is summarized. Virtually all immune cells studied show a combination of an activated status and loss of function. However, uremia preferentially decreases the number and function of lymphoid cells while myeloid cells show normal and/or elevated cell numbers with increased production of inflammatory cytokines and reactive oxygen species. These particular changes are compatible with immunological aging, which is characterized by loss of thymic function, attrition of telomeres and an expanded memory T cell population. Similar to aging in healthy individuals, the proinflammatory and potential cardiotoxic subsets of CD28^null T cells and CD16⁺ monocytes are increased. Epigenetically changed hematopoietic stem cells may be involved in immunological aging as specific DNA regions become hypermethylated. Proinflammatory T cells and monocytes persist after kidney transplantation, which constitutes a persistent cardiovascular risk factor. Possible therapeutic options to reverse or halt uremia-associated immunological aging are discussed. <b><i>Key Messages:</i></b> Premature aging of the immune system is a dominant feature in patients with end-stage renal failure, which corresponds to immunological aging in elderly healthy individuals, which is characterized by preferential loss of cells belonging to the lymphoid cell lineage, inflammation and expansion of proinflammatory immune cells.