Are monocyte subtypes (CD14 and CD16) precursors of early engraftment in allogeneic and autologous stem cell transplantation?

Introduction and Aim: Haematopoietic stem cell transplantation is a treatment method in which all haematopoiesis and immune system are renewed with donor cells. Malignant and benign haematological diseases are indications for haematopoietic stem cell transplantation. Monocytes are the first cells to engraft after transplantation, followed rapidly by neutrophils, platelets and natural killer (NK) cells. In the literature, there are studies on monocyte elevation a few days before neutrophil engraftment after haematopoietic stem cell transplantation. The aim of our study was to investigate whether monocytes and their subtypes (CD14 and CD16) are early precursors of engraftment after allogeneic and autologous peripheral blood stem cell transplantation in our haematopoietic stem cell transplantation centre. Materials and Methods: Between 1 July 2022 and 31 May 2023, 56 patients with allogeneic and autologous peripheral blood stem cell transplantation who met the exclusion and inclusion criteria were included in the study. The study was evaluated according to haemogram and biochemistry test results from the first day after transplantation until neutrophil and platelet engraftment. Engraftment days were recorded according to the haemogram test analysing blood cells. After transplantation, the day on which the monocyte value increased suddenly before engraftment was determined as the monocyte engraftment day and fluocytometry was performed with peripheral blood sample on monocyte engraftment days. Percentages of total monocytes and their subtypes CD14 and CD16 and lymphocytes and their subtypes CD3, CD4, CD8, CD19 and CD27 were analysed. Peripheral stem cell markers and immunophenotypic analyses were performed by flow cytometer method on naviosex (Beckman Coulter, Ireland). Results: Between 1 July 2022 and 31 May 2023, 56 allogeneic and autologous peripheral blood stem cell transplant patients admitted to Mersin University Medical Faculty Hospital Hematology Bone Marrow Transplant Centre were included in the study. The minimum age of the total patients was 19 years and the maximum age was 72 years. In terms of gender distribution, 57.1% were male and 42.9% were female. Allogeneic transplantation was performed in 42.9% and autologous transplantation in 57.1% of the patients. Multiple myeloma was diagnosed in 50%, acute myeloid leukaemia in 30.42%, hodgkin lymphoma, burkitt lymphoma, B-cell nonhodgkin lymphoma and T-cell acute lymphoblastic leukaemia in 1.8%, mantle cell lymphoma and B-cell acute lymphoblastic leukaemia in 3.6%, and myelodysplastic syndrome in 5.4%. Early posttransplant complications were observed in 57.1% of the patients. During the transplantation process, 35.7% of the patients received parenteral antibiotic treatment. In autologous peripheral blood stem cell transplant patients, cyclophosphamide-granulocyte-colony stimulating factor (GCSF) was used as mobilisation regimen in 71.9%, plerixafor-GCSF in 18.8% and etoposide-GCSF in 9.3%. The relationship between the highest serum monocyte percentage before engraftment and the day of platelet and neutrophil engraftment was significant (p<0,05). The day with the highest serum monocyte percentage occurred later in allogeneic peripheral blood stem cell transplantation than in autologous peripheral blood stem cell transplantation (p<0,05). There was no significant correlation between gender and age and serum monocyte percentage and subtypes of CD14 and CD16 on the day the flow cytometer was sent (p>0,05). No significant correlation was found between the percentage of serum monocytes and their subtypes CD14 and CD16 on the day the flow cytometer was sent according to mobilisation regimen (p>0,05). Conclusion: There was a positive correlation between monocyte engraftment days and platelet and neutrophil engraftment days. The use of cyclophosphamide-GCSF, plerixafor-GCSF and etoposide- GCSF as mobilisation regimens in autologous peripheral blood stem cell transplantation did not affect the percentage of serum monocytes and monocyte subtypes CD14 and CD16 on the day of flow cytometer delivery. The development of early posttransplant complications and parenteral antibiotic use did not affect the percentage of monocyte subtypes CD14 and CD16 and the days of neutrophil and platelet engraftment. Keywords: Haematological malignancy, bone marrow transplantation, engraftment