Immunosenescence is the name give to the age-related decline in effectiveness of the immune system. Some authors consider this to be distinct from inflammaging, the growth in chronic inflammation due to overactivation of the immune system in response to molecular damage and the presence of senescent cells, while others consider that chronic inflammation to be an aspect of immunosenescence. In today’s open access paper, researchers review immunosenescence from the perspective of the adaptive immune system, here meaning detrimental changes in T cell populations. The contributing causes of these changes are given as (a) the atrophy of the thymus, (b) a growing bias towards production of myeloid rather than lymphoid cells in the bone marrow, and (c) the burden of persistent infection, particularly cytomegalovirus.
The progressive age-related atrophy of the thymus, known as thymic involution, may be the most important of these issues. Thymocytes created in the bone marrow migrate to the thymus, where they mature into T cells. As active thymic tissue is replaced with fat, the supply of new T cells diminishes. While the overall number of T cells remains much the same throughout life, these cells become increasingly dysfunctional
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