Phenotype of NK Cells Determined on the Basis of Selected Immunological Parameters in Children Treated due to Acute Lymphoblastic Leukemia

Higher baseline natural killer cell counts are associated with a lower 8-day blast count and lower day 33 minimal residual disease in children with pediatric B-acute lymphoblastic leukemia

INTRODUCTION

Acute lymphoblastic leukemia (ALL) is the most common malignancy in children. Despite advancements in treatment, a significant proportion of children relapse. Recently, immunotherapy has gained momentum and is becoming popular, especially for relapsed and refractory cases. NK cells are an important part of tumor immunity and are involved in the direct killing of tumor cells. Their role in B-ALL has not been explored. Therefore, this study was conducted to correlate the number of NK cells with standard prognostic parameters in B-ALL.

METHODS

25 subjects with newly diagnosed B-ALL between 0-14 years were recruited for the study from Pediatric OPD or emergency of the hospital. Along with a complete hemogram and peripheral smear examination, immunophenotyping by flow cytometry was done at the time of diagnosis for NK cell enumeration. The number of NK cells was correlated with standard prognostic parameters using the spearman correlation coefficient.

RESULTS

Baseline NK cell percentage demonstrated a significant negative correlation with Prednisone poor day 8 blast response (P value = 0.02, r value = -0.44) and positive MRD (P value = 0.01, r value = -0.49) at day 33. A negative correlation was also noticed between NK cell percentage and unfavorable cytogenetics (hypodiploidy), although it was not significant (P value = 0.06, r value = -0.38). The number of NK cells did not correlate with age, gender and WBC count. Therefore, evaluating NK cells at diagnosis may serve as a simple and useful parameter for prognostication and risk stratification.

CONCLUSION

It may be assumed that a higher percentage of NK cells is associated with improved outcomes and probably a better prognosis. NK numbers may serve as an early independent parameter predicting prognosis and survival in children with B-ALL, thus helping to decide individual therapeutic regimens.

Residual Bone Marrow T & NK-Cells at Diagnosis in Pediatric Pre-B-ALL: A Case-Control Study

Background

Mature bone marrow T lymphocytes and NK may have a special relevance in the control of the malignant growth.

Objective

We aimed to assess the percentage of the residual BM T-cells, (T-helper -T-cytotoxic- NKT) and the NK cells of childhood precursor B-lymphoblastic leukemia (B-ALL) as an indicator of innate and adaptive immunity in these patients.

Subjects and Methods

This study was conducted on 40 B-ALL patients, and 40 apparently healthy matched children served as a control group. The flow cytometry was used to assess the percentage of the residual BM T-cells (T-helper, T-cytotoxic and NKT), and the NK cells.

Results

Compared with the control group, the percentage of the residual BM T-cells, its subtypes (T-helper, T-cytotoxic), and NKT cells in addition to the NK cells was significantly decreased in Group IA, and Group IB, but there was no significant difference between Group IA and Group IB in all studied parameters. In terms of the CD4/CD8 ratio, there was a significant increase in Group IA as compared to the control group (P < 0.026), but there were no significant statistical differences in CD4/CD8 ratio between Groups IB, and the control. Likewise, in CD4/CD8 ratio between groups IA, and Groups IB (P > 0.05). The percentage of NK, and NKT cells shows a significant increase in Hepatomegaly and Splenomegaly, as compared to non-Hepatomegaly and non-Splenomegaly patients of Groups IB (P < 0.05). However, there was a significant increase in statistical differences in the percentage of NKT cell between non-Splenomegaly, as compared to Splenomegaly patients of Group IA (P < 0.05). Additionally, there is a negative correlation between B.M Blast% to CD4/CD8 ratio and NK%, but there is no significant correlation between B.M Blast% to NK T% in the group 1 A.

NK Cells as Possible Prognostic Factor in Childhood Acute Lymphoblastic Leukemia

Deficiency or impaired function natural killer (NK) cells might result in the development of serious infections and promote the development of malignancies. The aim of our study was to assess the prognostic role of NK cell percentage in bone marrow on the day of acute lymphoblastic leukemia (ALL) diagnosis. 84 children (49 males = 58%; median age 5 yrs) with ALL were enrolled. The NK cell percentage was assessed using flow cytometry with antibodies against the cluster of differentiation (CD): CD3, CD56, and CD16. We evaluated two groups: group I (NK+), patients with NK cells in the bone marrow (n = 74), and group II (NK-), patients without NK cells in the bone marrow (n = 10) (cut-off value of negative <1%). In the patients from group I, the prednisone good response on day 8 and the remission on day 15 of treatment were observed significantly more often (p = .01, p = .03). The children from group I had significantly better survival as compared to those from group II (p = .02) (HR 2.59; 95% CI: 1.38-4.85). The presence of NK cells in the bone marrow at diagnosis can be a prognostic factor in children with ALL. The presented results should be the basis for further research.

NK cell-mediated anti-leukemia cytotoxicity is enhanced using a NKG2D ligand MICA and anti-CD20 scfv chimeric protein

NK cells are important innate cytotoxic lymphocytes that have potential in treatment of leukemia. Engagement of NKG2D receptor on NK cells enhances the target cytotoxicity. Here, we produced a fusion protein consisting of the extracellular domain of the NKG2D ligand MICA and the anti-CD20 single-chain variable fragment (scfv). This recombinant protein is capable of binding both NK cells and CD20⁺ tumor cells. Using a human NKG2D reporter cell system we developed, we showed that this fusion protein could decorate CD20⁺ tumor cells with MICA extracellular domain and activate NK through NKG2D. We further demonstrated that this protein could specifically induce the ability of a NK cell line (NKL) and primary NK cells to lyse CD20⁺ leukemia cells. Moreover, we found that downregulation of surface HLA class I expression in the target cells improved NKL-mediated killing. Our results demonstrated that this recombinant protein specifically lyses leukemia cells by NK cells, which may lead to development of a novel strategy for treating leukemia and other tumors.