PB2387 CD56 BRIGHT/CD16‐ NATURAL KILLER CELLS COUNTS ARE HIGHER IN THE UMBILICAL CORD BLOOD THAN IN THE PERIPHERAL BLOOD FROM ADULTS
Authors: Barbosa M. , Molla V. , Junior A. Mendroni , Goncalves M. , Kimura E. , Guirao F. , Yamamoto M. , Arrais‐Rodrigues C. 
Published: June 2019

Background:Umbilical cord blood (UCB) is an alternative source of hematopoietic stem cells for allogeneic transplantation in the absence of compatible donor. UCB transplantation has lower incidence of chronic graft versus host disease (GvHD) but is associated with slower engraftment and slower immune reconstitution as compared to other sources. Dendritic cells (DC) and Natural Killer cells (NK) play a central role in the development of GVHD, the graft versus leukemia (GvL) effect, and in the control of infectious complications.Aims:To compare the absolute counts and frequencies of monocytes, B lymphocytes, T cells, NK cells and DC and their subsets in samples from UCB and PB.Methods:We quantified by multiparametric flow cytometry monocytes, B cells, T cells, NK cells and DC, including their subsets, in UCB samples from 54 healthy newborns and 25 peripheral blood (PB) samples from healthy adult volunteers [median age 33 years (range 18 to 66 years old); 15 (60%) male]. Fresh EDTA‐anticoagulated PB or UCB samples were collected and processed in up to 24 hours, using an 8‐color monoclonal antibodies panel (CD16 FITC/ CD56 & CD4 PE/ CD11c PerCP Cy5.5/ CD8 & CD19 PC7/ CD123 APC/ CD3 & CD14 APC‐H7/ HLA‐DR Pac Blue/ CD45 OC‐515), by stain‐lyse‐wash method. Acquisition was performed through FACSCANTOII flow cytometer and FACsDIVA® software (BDB‐ San Jose, CA). For data analysis Infinicity® software (Cytognos, SL) was used. NK cells (CD3‐, CD19‐, CD14‐, and CD56+), were classified as CD56brightCD16− or CD56dimCD16bright. Monocytes (CD45+, CD11c+, and HLA‐DR+) were classified as: classic (CD14++CD16‐), intermediate (CD14++CD16+) and non‐classical (CD14dimCD16++). Dendritic cells (HLA‐DR++, CD3‐, CD19‐, CD14‐, and CD56‐) were classified as pDC (CD123+/ CD11c‐), and mDC (CD123‐/ CD11c++). B cells were identified by CD19+ and absence of T and monocytic line markers. Comparisons between UCB and PB were performed using Mann‐Whitney test through SPSS version 21.0 (SPSS Inc., Chicago, IL). P value of <.05 was considered significant.Results:In the UCB samples, as compared to the PB samples, there were higher counts of NK CD56brightCD16− NK cells (median 0.24 × 108/L vs. 0.12 × 108/L, respectively, P < 0.0001), NK CD56dimCD16bright NK cells (median 4.46 × 108/L vs. 2.59 × 108/L, respectively, P = 0.001), and plasmacytoid dendritic cells (pDC, median 0.08 × 108/L vs. 0.06 × 108/L, respectively, P = 0.03). However, non‐classical monocytes counts were lower in UCB than in PB (We also observed lower counts of non‐classical monocytes (0.24 × 108/L vs. 0.51 × 108/L, respectively, p < .0001).Summary/Conclusion:In conclusion, our results show there were higher counts of NK cells and pDC and lower counts of non‐classical monocytes in UCB than in PB from healthy individuals. These findings might explain the lower incidence and severity of chronic GVHD although maintaining the GVL effect in UCB transplants recipients as compared to other stem cell sources.