The aging immune system and its relationship with cancer

Abstract

The incidence of most common cancers increases with age. This occurs in association with, and is possibly caused by a decline in immune function, termed immune senescence. Although the size of the T-cell compartment is quantitatively maintained into older age, several deleterious changes (including significant changes to T-cell subsets) occur over time that significantly impair immunity. This article highlights some of the recent findings regarding the aging immune system, with an emphasis on the T-cell compartment and its role in cancer.

Figure 1. Age-associated changes characteristic of immunosenescence occur in T-cell populations

The young thymus supports more robust thymopoiesis with naive cells, which have the greatest T-cell receptor repertoire diversity and comprise the largest proportion of T cells. With aging, thymus involution occurs and there is progressive loss of T-cell receptor repertoire diversity with the decreased population of naive T cells and there is an enlarged memory component that secretes most type 1 and 2 cytokines. With repeated stimulation, the memory cells give rise to activated effector T cells, which are oligoclonal and have the most restricted T-cell receptor repertoire.