The frequencies of lymphocyte subsets on "day 30″ correlate with the clinical outcome of pediatric hematopoietic stem cell transplantation.

We aimed to determine the relationship between lymphocyte subsets on day 30 (D30) and prognosis after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in children. We retrospectively examined the clinical outcomes and lymphocyte subsets on D30 after allo-HSCT in 115 pediatric patients at the Children's Hospital of Soochow University between January 2016 and June 2019. Measurements were performed using flow cytometry on D30. Lymphocyte subsets were compared among the umbilical cord blood (UCB) (n = 22), HLA-matched sibling donor (MSD) (n = 14), haploidentical donor transplantation (HID) (n = 57), and unrelated donor transplantation (UD) (n = 22) groups. The relationships between the frequencies and counts of lymphocyte subsets and clinical outcomes were analyzed. T and B cell counts were the highest in the MSD group compared to the other groups, and natural killer cell counts were the highest in the UCB group. Lymphocyte subsets on D30 after allo-HSCT were correlated with the occurrence of acute (aGVHD) and chronic graft versus host disease (cGVHD). A high frequency of B cells (≥4.65%) was associated with the development of severe aGVHD. High frequencies of CD4+ T (≥10.25%) were correlated with extensive cGVHD. Moreover, a high frequency of CD4+ T cells (≥9.80%) was correlated with GVHD-free and failure-free survival (GFFS) after allo-HSCT. However, on D30, there were no statistically significant correlations between viral infections and lymphocyte subsets. The frequencies of lymphocyte subsets on D30 after allo-HSCT are good indicators of prognosis after allo-HSCT in children.