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.

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## Study
- 1 97 hematologically normal females
	- 23 newborn
	- 94 young adult (median 30)
	- 80 eldery (over 75)
- purified neutrofils
- purified T-cells
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### Metoder
1. Peripheral blood samples were collected
2. Neutrophils and T cells were isolated using cell separation techniques _(centrifugation followed by lineage-specific purification)_
3. X-chromosome inactivation was analyzed using the HUMARA PCR assay _(PCR-based measurement of which X chromosome is active)_
4. T cells were analyzed by PCR to check for clonal expansion _(T-cell receptor γ gene rearrangement analysis)_
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### Results
1. X chromosome usage is similar in newborns and young adults.
2. Neutrophils from elderly female individuals show strongly uneven X chromosome usage.
3. T-cells show much less uneven X chromosome usage and no dominant clonal expansion
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### Cord blood neutrophils
![[image-183.png|148x156]] 
<small>
- Graph shows the distribution of X chromosome usage in 23 newborn
- X-axis: % of cells using the less common X chromosome.
- Y-axis: number of individuals in each group.
Conclusion: Newborns mostly show balanced use of the two X chromosomes
</small>

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### > 75 years neutrophils

![[image-184.png|145x158]]
<small>
- 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.
</small> 
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### Questions
- What was the main question the authors wanted to answer?
- Why did they choose this specific method instead of another one?
- What does this figure show in one sentence?
- What is the main conclusion from your article?
- What would be the biggest limitation of this study?