Neutrophil Extracellular Traps Formation Post-hematopoietic Stem Cell Transplantation (NETs post HSCT)

Although neutrophil engraftment takes place 10 to 14 days after autologous HSCT, and 15 to 30 days after allogeneic HSCT, using an ablative conditioning regimen, neutrophil dysfunction may persist for longer periods. Relatively scant data exists on neutrophil function following HSCT. After autologous HSCT, the respiratory burst and phagocytosis may be decreased for up to 3 months. After allogeneic HSCT, respiratory burst and chemotaxis are generally decreased for 4 to 6 months. Factors such as continuation of chemotherapy, immunosuppression, and GVHD contribute to this prolonged dysfunction. No data exist on reconstitution of NETs following HSCT.

Nets production and other neutrophil functions will be examined at several time points: before transplantation, at neutrophil engraftment, 6 weeks, 3 months, 6 months, 9 months, 1 year, 1.5 years, 2 years, and 3 years post-transplant, or until normalization of neutrophil function at 2 consecutive time points. Data gathered on patients will cover:

1. Demographics.
2. Tumor histological type, staging, previous chemotherapy regimen, and initial response to treatment.
3. HSCT procedure - type of conditioning regimen, type of graft (autologous or allogeneic - related donor/unrelated donor/cord blood), use of bone marrow stem cells (SCs) or peripheral mobilized SCs, number of SCs given, post-transplant immunosuppression, post-transplant prophylactic antimicrobial treatment, infections during the study period, and GVHD occurrence and treatment.

Neutrophil examinations will be done in collaboration with the Laboratory for Leukocyte Function of the Department of Pediatrics, Meir Medical Center, Kfar Saba and NETs visualization with the Department of Cellular Microbiology at the Max Planck Institute for Infection Biology, Berlin.