Age-associated accumulation of CMV-specific CD8+ T cells expressing the inhibitory killer cell lectin-like receptor G1 (KLRG1).
Level 4 - case-series / case-control
Cross-sectional comparative laboratory study using human donor blood samples
PubMed 12915213 · doi:10.1016/s0531-5565(03)00134-7
What was done
Peripheral blood CD8+ T cells from young and old human donors were analyzed for the expression of the inhibitory killer cell lectin-like receptor G1 (KLRG1), a marker of replicative senescence. Tetramer staining was used to assess CMV-specific CD8+ T cells expressing KLRG1, and functional capacity was measured by the fraction of cells secreting interferon-gamma following specific antigenic stimulation.
What was found
The frequency of CD8+ T cells expressing KLRG1 was elevated in CD8+ T cells from older donors compared to younger donors. Tetramer staining showed that the elevated frequency of CMV-specific CD8+ T cells in the elderly was due to an accumulation of cells bearing KLRG1. The fraction of CMV-specific T cells able to secrete interferon-gamma following antigenic stimulation was significantly lower in the elderly than in the young, although the total number of functional cells was comparable. The abstract reports no numerical values, exact sample sizes, or p-values.
Why it matters
The findings indicate that age-associated clonal expansions of CMV-specific CD8+ T cells primarily consist of replicatively senescent, dysfunctional cells. This accumulation may restrict the T-cell repertoire available for other pathogens in older adults.
Limits
The abstract does not provide sample sizes, precise age ranges, or quantitative statistics (percentages, effect sizes, confidence intervals). The cross-sectional design cannot establish direct causality between these cellular changes and clinical infection risk.
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.