Large numbers of dysfunctional CD8+ T lymphocytes bearing receptors for a single dominant CMV epitope in the very old.
Level 4 - case-series / case-control
Cross-sectional observational comparison between young and elderly individuals without clinical intervention
PubMed 12959217 · doi:10.1023/a:1024580531705
What was done
Using MHC-peptide tetramer technology, the authors analyzed peripheral CD8+ T lymphocytes specific to a single cytomegalovirus (CMV) epitope, comparing very elderly individuals (>85 years) to younger controls. They assessed epitope-specific T-cell numbers, CD28 expression, and functional capacity measured by interferon-gamma (IFN-γ) secretion following antigenic stimulation.
What was found
The abstract reports no exact numbers, percentages, or effect sizes. It reports that very elderly individuals had markedly higher numbers of CD8+ T cells specific for a single CMV epitope. Compared to younger individuals, these tetramer-reactive CD8+ T cells in the elderly had a significantly lower percentage of CD28 expression and a significantly lower fraction secreting IFN-γ after specific stimulation.
Why it matters
This study provides cellular-level evidence that massive, dysfunctional clonal expansions of CMV-specific CD8+ T cells occur in extreme old age, which may constrict the naive T-cell repertoire available for other pathogens.
Limits
The abstract reports no sample sizes (n is unknown), no quantitative measurements, no p-values, and no details on participant health status or selection criteria. The cross-sectional design demonstrates phenotypic and functional differences but cannot prove a causal relationship with susceptibility to other infections.
Cited by
- supports In old age, individuals accumulate CMV-specific T cells, which in some individuals can expand to occupy 20% to 30% of all T cells dedicated to a single CMV peptide.