# Regeneration of Peripheral Blood T-Cell Subpopulations in Children After Completion of Acute Lymphoblastic Leukemia Treatment

## TL;DR

This study shows that children who completed ALL treatment have altered T-cell populations in their blood, indicating ongoing immune system recovery and possible chronic immune activation.

## Contribution

The study provides a detailed analysis of T-cell subpopulations in ALL survivors, revealing specific immune changes post-treatment.

## Key findings

- Children after ALL treatment had lower TCRγδ+ T cells and higher double-positive CD4+CD8+ T cells.
- Post-treatment patients showed increased memory and activated T-cell subpopulations.
- Total lymphocyte counts were higher in ALL survivors compared to healthy controls.

## Abstract

Childhood acute lymphoblastic leukemia (ALL) is the most common pediatric cancer, and while chemotherapy has significantly improved survival rates, it can also lead to long-term side effects, including immune system dysfunction. This study aimed to investigate in detail, using flow cytometry, the T-cell subpopulations in the peripheral blood of children who have completed ALL treatment and compare them to a group of healthy children. The study group consisted of 20 patients, aged 5 to 18 years, with blood samples collected at least one year after treatment completion. Of the 52 T-cell subpopulations analyzed, 16 showed statistically significant differences. Children after ALL treatment had lower absolute values of TCRγδ+ and higher values of double-positive CD4+CD8+ and CD8+ T cells. They also had higher absolute numbers of memory T cells, including total CD45RO+ T cells, and the CD45RO+CD8+ and CD45RO+CD27+ subpopulations. Furthermore, post treatment patients showed higher absolute values of activated T cells (HLA-DR+, HLA-DR+CD8+, HLA-DR+CD57+, and CD25+CD8+), as well as CD57+ and CCR7+ T cells. The absolute leukocyte and granulocyte counts were lower in the study group, while the total lymphocyte count was significantly higher compared to the control group. The findings indicate persistent changes in T-cell subpopulations after ALL treatment, suggesting ongoing immune system rebuilding and chronic antigenic stimulation, possibly due to viral reactivation or chemotherapy-related tissue damage. The increased number of TCRγδ+ cells, which are responsible for eliminating cancer cells, may be a positive aspect of this rebuilding.