Features of the leukocyte pool of umbilical cell blood cell concentrate prepared for long-term cryostorage

Allogeneic hematopoietic cell transplantation is the standard of care for patients with highrisk acute leukemia. Cord blood (UCB) is an alternative source of allogeneic hematopoietic stem cells for patients who need transplantation but do not have a related donor. The purpose of our study was to evaluate the characteristics of leukocyte pool (cellular composition, immunophenotype) of umbilical cord blood (UCB) cell concentrates, which were harvested for public long-term cryostorage for the needs of transplantology. A study of 1096 samples of umbilical cord blood of full-term newborns before and after processing [isolation of hematopoietic stem cells (HSC) concentrate] was carried out. The number of cells in the pooled concentrate of HSC at a volume of 25 mL, after long-term cryostorage was as follows: leukocytes, 17.41±0.36 × 10 8 ; HSCs with CD34 + immunophenotype, 5.25±3.6 × 10 6 ; natural killer cells (CD3-CD16 + CD56 + ), 1.65 + 0.7 × 10 8 . Analysis of the NKT cell population revealed 6.22±2.1% of cells with CD3 + CD16/CD56 + immunophenotype. The contents of CD3 + CD56 + cells was 2.69±2.4%, the relative amount of CD3 + CD16 + was 2.53±1.2%. In the pooled NKT cell preparations, 5.15±2.1% of CD56 + CD16 cells were detected, and two minor subpopulations were also identified, which differ in CD56 and CD16 antigen expression: the level of CD56 - CD16 + was 2.91±1.2%, and the ratio of CD56 + CD16 + cells was 0.69±0.3%. The obtained data on relative amounts and characteristics of cellular immunophenotype as well as the heterogeneity of the NK and NKT cell population in the HSC UCB concentrate, subjected to long-term cryostorage must be taken into account when selecting the HSC UCB concentrates for the purpose of transplantation in oncohematological diseases.