Johan Dahlin
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The aim of the study was to investigate whether normal aging leads to blood cells being produced from fewer cell clones. This was examined by comparing which X chromosome the cells were using between different age groups and between neutrophils and T cells.
In other words, they studied human hematopoiesis across age by analyzing purified blood cell lineages from the subjects.
Modell/material
- 197 hematologically normal females
- 23 new born
- 94 young adult (median 30)
- 80 eldery (over 75)
- purified neutrofils
- purified T-cells
Methods
- Peripheral blood samples were collected
- Neutrophils and T cells were isolated using cell separation techniques (centrifugation followed by lineage-specific purification)
- X-chromosome inactivation was analyzed using the HUMARA PCR assay (PCR-based measurement of which X chromosome is active)
- T cells were analyzed by PCR to check for clonal expansion (T-cell receptor γ gene rearrangement analysis)
Results
- X chromosome usage is similar in newborns and young adults.
- Neutrophils from elderly female individuals show strongly uneven X chromosome usage.
- T-cells show much less uneven X chromosome usage and no dominant clonal expansion
Figure
!image-183.png Notes
- This graph shows the distribution of X chromosome usage in 23 newborn females
- X-axis: the % of cells using the less common X chromosome.
- 50% means perfectly (50% maternal / 50% paternal)
- 0/100% means all cells use the same chromosome
- Y-axis: number of individuals in each group
Conclusion:
- Newborns mostly show balanced use of the two X chromosomes.
!image-184.png Notes
- This graph shows the purified neutrofils from 80 elderly (y >= 75) females
- X and Y axis is the same as in previous graph
Conclusion:
- Elderly neutrophils frequently show strongly uneven X chromosome usage.