Thymic involution in aging

J Clin Immunol. 2000 Jul;20(4):250-6. doi: 10.1023/a:1006611518223.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Aged
  • Aging / immunology*
  • Aging / pathology
  • Animals
  • Atrophy
  • Forecasting
  • Hematopoiesis / physiology
  • Hematopoietic Stem Cells / pathology
  • Humans
  • Immunotherapy
  • Interleukin-7 / therapeutic use
  • Mice
  • Mice, Knockout
  • Mice, Transgenic
  • Recombinant Proteins / therapeutic use
  • Stromal Cells / pathology
  • T-Lymphocyte Subsets / cytology*
  • Thymus Gland / growth & development*
  • Thymus Gland / immunology
  • Thymus Gland / pathology

Substances

  • Interleukin-7
  • Recombinant Proteins