Memory Cells & Senescent Cells
Many quantitative and qualitative changes occur in the memory cell compartment. As discussed above, parallel to the reduction in naive cells during aging, there is an accumulation of effector memory T cells. The continuous antigenic stimulation and associated clonal expansion and differentiation of effector T cells lead to the appearance of senescent T cells, as identified by the expression of the surface receptors CD57 and KLRG1, absence of the expression of the costimulatory molecule CD28 and erosion of the telomeric region due to successive replicative cycles during immunological responses.
Telomere erosion is associated with increased resistance to apoptosis, allowing the accumulation of these senescent cells with high proinflammatory profiles in blood and tissues, and its contribution to many age-related diseases characterized by an inflammatory background. In addition, changes in the pattern of cytokine secretion were detected in cultures of CD8+ senescent T lymphocytes (CD28−), including an increase in TNF-α and IL-6 and decrease in IFN-γ and IL-2 secretion, showing that CD28 is essential for the stabilization of many cytokines.
Immunotherapy. 2013;5(8):879-893. © 2013 Future Medicine Ltd.