Lymphocyte subpopulations in children after allogenic stem cell transplantation

B a c k g r o u n d . Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a method of treatment in a variety of diseases, which involves replacing the recipient's bone marrow by healthy donor stem cells. O b j e c t i v e . The aim of the study was the analysis of immune reconstitution in children and adolescents after allo- HSCT. P a t i e n t s a n d m e t h o d s . We analyzed lymphocyte subpopulations in 67 children after allo-HSCT for hematological malignancies and non-malignant diseases. B-cells, T-cells, NK (natural killer cells) and CD4/CD8 ratio were assayed in peripheral blood by flow cytometry using a set of antibodies CD2/CD19, CD3/CD4/CD8, CD3/CD16CD56 labeled with different fluorescent dyes. The tests were performed at 1, 3, 6, 9, 12, 15, 18 and 24 months after the HSCT. R e s u l t s . Normalization of the number of lymphocytes occurred rapidly in the population of NK cells; however, significant decrease in the proportion of NK cells was observed at 6 months after HSCT (p=0.028). The recovery of T cells occurred after 3 months for CD2 and after 6 months for CD3 cells. Within the B-cell population, a significant delay of reconstitution was observed: CD19 cell percentage exceeded 5% (p<0.001) in the ninth month after HSCT, while it was above 10% afterwards. The normalization of CD4/CD8 ratio was very slow and delayed and did not achieve normal values within 24 months after allo-HSCT. C o n c l u s i o n s . Reconstitution of the immune system in children after allo-HSCT is the fastest for NK cells. Normal values of T- and B-lymphocytes were reached after 6 and 9 months, respectively. CD4/CD8 ratio is a parameter the normalization of which requires at least two years.