Thymic involution in aging.
The size of the naive T-cell pool is governed by output from the thymus and not by replication. This pool contributes cells to the activated/memory T-cell pool whose size can be increased through cell multiplication; both pools together constitute the peripheral T-cell pool. Aging is associated with involution of the thymus leading to a reduction in its contribution to the naive T-cell pool; however, despite this diminished thymic output, there is no significant decline in the total number of T cells in the peripheral T-cell pool. There are, however, considerable shifts in the ratios of both pools of cells, with an increase in the number of activated/memory T cells and the accumulation in older individuals of cells that fail to respond to stimuli as efficiently as T cells from younger individuals. Aging is also associated with a greater susceptibility to some infections and some cancers. An understanding of the causal mechanism of thymic involution could lead to the design of a rational therapy to reverse the loss of thymic tissue, renew thymic function, increase thymic output, and potentially improve immune function in aged individuals.
Aspinall
R
R
Department of Immunology, ICSTM at Chelsea and Westminster Hospital, London, England.
Andrew
D
D
D000368:Aged; D000375:Aging / Q000276:immunology* / Q000473:pathology; D000818:Animals; D001284:Atrophy; D005544:Forecasting; D006410:Hematopoiesis / Q000502:physiology; D006412:Hematopoietic Stem Cells / Q000473:pathology; D006801:Humans; D007167:Immunotherapy; D015851:Interleukin-7 / Q000627:therapeutic use; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D011994:Recombinant Proteins / Q000627:therapeutic use; D017154:Stromal Cells / Q000473:pathology; D016176:T-Lymphocyte Subsets / Q000166:cytology*; D013950:Thymus Gland / Q000254:growth & development* / Q000276:immunology / Q000473:pathology
D015851:Interleukin-7; D011994:Recombinant Proteins