1. Assess possibility of prediction of blood stream infections in ALL patients by profiling of NK cells using flow cytometry.
2. Assess the role of NK cells in development of drug resistance post chemotherapy.

Acute lymphoblastic leukemia (ALL) is the most common malignancy affecting children accounting for approximately 30% of childhood cancers (Zeng XL et al, 2023 ALL is characterized by chromosomal abnormalities and genetic alterations involved in the differentiation and proliferation of lymphoid precursor cells (Fujita, Sousa-Pereira et al. 2021).

ALL is categorized in B-Lymphoblastic Leukemia (B-ALL) And T-Lymphoblastic Leukemia (T-ALL), originated from B- and T-Lineage lymphoid precursor cells, respectively (Chiaretti S et al, 2014).

Recent progress in treatment of ALL has increased the survival rate significantly. The 5-year survival rate in children with ALL is approximately 90% (Paul 2016).

Bloodstream infection is a major cause of treatment-related morbidity and mortality in pediatric patients treated for acute lymphoblastic leukemia (Wolf, Tang et al. 2017).

This is caused by severe and prolonged immunosuppression due to neutropenia, and other chemotherapy-induced alterations of host defense mechanisms The rise of multidrug-resistant bacteria has generated a great challenge to treat infections caused by bacteria with the available antibiotics One of the crucial first line of defense against bloodstream infections in the immune system are Natural Killer cells Natural killer (NK) cells are lymphocytes of the innate immune system that are critical in host defense and immune regulation They can mediate spontaneous cytotoxicity towards malignant cells and microbes, and rapidly secrete numerous cytokines and chemokines to promote subsequent adaptive immune responses

NK cells can be subdivided into different populations based on the relative expression of the surface markers CD16 and CD56

Inclusion Criteria:

• Patients aged less than 17 years diagnosed as Acute Lymphoblastic Leukemia and on chemotherapy, who are positive for blood stream infection.

Exclusion Criteria:

1. Patients over 17 years of age.
2. Presence of other hematological malignancies or history of other malignancies.

Primary care clinic.