Evaluation of Lymphocyte Subpopulations in Cord Blood of Bulgarian Newborns

Umbilical cord blood (UCB) is a clinically useful source of hematopoietic stem and progenitor cells for treatment of a wide variety of malignant and non-malignant disorders. An important way to completing infor- mation on the quality and composition of units for transplantation is more extensive immunophenotyping of UCB. Moreover, phenotyping of lymphocyte subpopulations is essential for the diagnosis and follow-up of children with immunodeficiencies and other immune disorders and therefore, establishment of age-matched reference values of lymphocyte subsets is a necessity for each population. The aim of this study was to determine the normal range of T and B lymphocytes, and NK cells as well as the CD4 and CD8 subpopulations of T cells in cord blood collected from healthy term infants.The relative and absolute number distributions (median, 5th and 95th percentile) of lymphocyte subsets in cord blood samples from 72 healthy newborns were examined by multi-colour flow cytometry with a view to obtaining reference values for Bulgarian neonates at birth.Mean percentages of lymphocyte subpopulations were: CD3 (62.27 ± 9.64), CD19 (17.47 ± 5.46), CD3- CD16/CD56+ (17.27 ± 8.4). Our results show the prevalence of helper-inducer CD3+CD4+ (44.88-8.21) compared to the suppressor-cytotoxic CD3+CD8+ (16.65 ± 4.54) T-cell subpopulation, which determines the positive CD4/CD8 ratio (2.86 ± 0.82; 1.4-4.8). Also, the absolute numbers of studied populations varied widely due to differences of the absolute number of lymphocytes in the samples.This study on distribution of lymphocyte subpopulations in UCB helps to enhance our knowledge about cell phenotypes in cord blood and improve characterization of products for cellular therapy, as well as contributes to the correct interpretation of laboratory results for infants with possible immune disorders. Our data can be used as normal intervals for lymphocyte subsets in Bulgarian neonates.