Reduction in Proportion of Senescent CD8+ T Lymphocytes During Chemotherapy of Children with Acute Lymphoblastic Leukemia.

Aim: To evaluate quantitative changes in B, NK and T lymphocyte subsets in peripheral blood of children with acute lymphoblastic leukemia (ALL) undergoing chemotherapy. Patients and Methods: Children with ALL were treated according to NOPHO ALL 2008 protocol. Levels of B lymphocytes (CD19(+)), NK cells (CD3(-)CD56(+)) and subsets of T lymphocytes (CD3(+)CD4(+), CD4(+)CD25(+)Foxp3(+), CD3(+)CD8(+), CD3(+)CD8(+)CD57(+), CD3(+)CD8(+)CD57(-)) in peripheral blood were analyzed by flow cytometry prior and during treatment with cytotoxic drugs. Results: Immunological analyses were performed in 25 children with ALL. Levels of B and NK lymphocytes decreased continuously during chemotherapy. In contrast, levels of most T lymphocyte subsets decreased only transiently and returned to pretreatment levels by days 78 to 85. The only T lymphocyte subset that did not return to the pretreatment level contained senescent CD3(+)CD8(+)CD57(+) lymphocytes. Conclusion: Immunomodulating action of chemotherapy in children with ALL results in reduction of proportion of senescent CD8(+) T lymphocytes.