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Updated: Aug 15, 2026

Quantitative Imaging of Lineage-specific Toll-like Receptor-mediated Signaling in Monocytes and Dendritic Cells from Small Samples of Human Blood
Published on: April 16, 2012
Changes in the aging immune system
1Institute for Biomedical Aging Research, Austrian Academy of Sciences, Innsbruck, Austria.
The functional capacity of the immune system gradually declines with age. T lymphocytes are more severely affected than B cells or antigen-presenting cells. This is mainly due to the involution of the thymus which is almost complete at the age of 60. The host is then dependent on the T cell pool generated in earlier life. Continuous activation, clonal expansion and elimination of T cells of various specificities eventually leads to changes in the T cell repertoire. CD45RA+ "naive" cells are replaced by CD45RA- "memory" cells and a T cell receptor oligoclonality develops. At the same time, T cells with signal transduction defects accumulate. Age-related T cell alterations lead to a decreased clonal expansion and a reduced efficiency of T cell effector functions such as cytotoxicity or B cell help. Decreased antibody production and a shortened immunological memory are the consequence. Changes in the aging immune system represent a permissive factor for the frequent occurrence and the severity of disease. Efficient protection of elderly individuals by suitable vaccination strategies is therefore a matter of great importance.
The functional capacity of the immune system gradually declines with age. T lymphocytes are more severely affected than B cells or antigen-presenting cells. This is mainly due to the involution of the thymus which is almost complete at the age of 60. The host is then dependent on the T cell pool generated in earlier life. Continuous activation, clonal expansion and elimination of T cells of various specificities eventually leads to changes in the T cell repertoire. CD45RA+ "naive" cells are replaced by CD45RA- "memory" cells and a T cell receptor oligoclonality develops. At the same time, T cells with signal transduction defects accumulate. Age-related T cell alterations lead to a decreased clonal expansion and a reduced efficiency of T cell effector functions such as cytotoxicity or B cell help. Decreased antibody production and a shortened immunological memory are the consequence. Changes in the aging immune system represent a permissive factor for the frequent occurrence and the severity of disease. Efficient protection of elderly individuals by suitable vaccination strategies is therefore a matter of great importance.
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