Objective: The aim of this study was to investigate changes in natural killer (NK) cell
proportion, NK cell activity, and cytokine levels in children with acute lymphoblastic leukemia
(ALL) during and after therapy.
Materials and Methods: The study group included 33 ALL patients and the control group
consisted of 11 healthy children. The ALL patients were divided into three groups, those who
had completed protocol M, receiving maintenance chemotherapy, and whose chemotherapy was
discontinued. NK cell cytotoxicity was evaluated at different effector to target (E:T) cell ratios
and in lytic units (LU). Expression of CD56, CD3, NKp46, CD2, CD94, NKG2D, and CD16
molecules and levels of the interferon gamma (IFN-γ) and interleukin-15 (IL-15) were measured.
Results: NK cell activity at an E:T ratio of 1:1 was higher in patients receiving maintenance
chemotherapy compared to the other groups (p<0.05), but there was no difference between
the groups in LU (p>0.05). The ratio of CD16+CD56+ cells was smaller in the maintenance
chemotherapy group compared to controls (p<0.05). Patients who underwent prophylactic
cranial irradiation showed significantly higher NK cytotoxicity at 1:1 E:T ratio compared to
those who did not (p<0.05). Eighty-three percent of patients in the maintenance chemotherapy
group underwent prophylactic cranial irradiation. The IFN-γ levels were significantly lower in
the maintenance chemotherapy and discontinued treatment groups compared to the control
Conclusion: In children with ALL, chemotherapy reduces the NK cell population and IFN-γ
levels. The increase in NK cell activity in patients receiving maintenance chemotherapy may be
associated with prophylactic cranial radiotherapy.
Keywords: Acute lymphoblastic leukemia, children, interferon, natural killer cells