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Updated: Jul 10, 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
Early activation defects in T lymphocytes from aged mice
R A Miller1, G Garcia, C J Kirk
1Department of Pathology, University of Michigan, Ann Arbor, USA. millerr@umich.edu
Abstract:
Aging affects both calcium signals and protein kinase cascades in mouse T lymphocytes. The decline in calcium signal development largely represents differences between naive and memory T cells; the latter are resistant to increases in calcium concentration, and are more common in aged mice. Aging leads to declines in phosphorylation of a wide range of substrates in T cells stimulated by either anti-CD3 antibodies or by substances, such as phorbol myristate acetate (PMA) or ionomycin, that act at intracellular sites, but some phosphoproteins respond only in old T cells, and others respond regardless of age. Tyrosine phosphorylation of the CD3 zeta chain declines with age, both in resting T cells and after activation, but the proportion of Zap-70 that is bound to CD3 zeta increases in T cells from old mice. Zap-70 function and phosphorylation of CD3 zeta-associated Zap-70 change only slightly after stimulation of T cells by anti-CD3 and anti-CD4, and are at similar levels in activated old and young T cells. Nonetheless, induction of Raf-1, MEK, and ERK kinase activity declines with age in CD4 T cells. The effect of aging on T-cell activation is not simply an overall decline in signal intensity, but a set of qualitative changes that differ among subsets and depend at least partly on the nature of the stimulus.
Insights
Aging alters mouse T lymphocyte signaling, with memory cells showing resistance to calcium increases. Kinase activity declines, indicating complex age-related changes in T-cell activation rather than a simple decrease in signal intensity.
Area of Science:
- Immunology
- Cellular Signaling
- Aging Research
Background:
- Aging impacts T lymphocyte function, affecting calcium signaling and protein kinase pathways.
- Naive and memory T cells exhibit distinct responses to stimuli, with memory cells being more prevalent and less responsive in aged individuals.
Purpose of the Study:
- To investigate the age-related changes in calcium signaling and protein kinase cascades within mouse T lymphocytes.
- To elucidate the qualitative and quantitative alterations in T-cell activation pathways due to aging.
Main Methods:
- Stimulation of T cells using anti-CD3 antibodies and intracellular activators like phorbol myristate acetate (PMA) and ionomycin.
- Analysis of protein phosphorylation, including tyrosine phosphorylation of CD3 zeta chain and Zap-70 binding.
- Assessment of kinase activity for Raf-1, MEK, and ERK in CD4 T cells.
Main Results:
- Aged T cells show altered calcium signal development, with memory cells being resistant to calcium increases.
- Declines in phosphorylation of various substrates were observed in T cells from aged mice upon stimulation.
- While Zap-70 function remained largely unchanged, the induction of Raf-1, MEK, and ERK kinase activity decreased with age in CD4 T cells.
Conclusions:
- Aging induces qualitative changes in T-cell activation, not just a general decline in signal intensity.
- These age-related changes are subset-specific and stimulus-dependent, highlighting the complexity of immune aging.
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