INTRODUCTION
Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potential treatment for many patients with malignant and non-malignant diseases. Although much improvement has been made during the past decades, several complications affecting patient survival or quality of life remain to be addressed.1
It is well established that immune reconstitution (IR) after HSCT is influenced by patient and transplant factors and strongly associated with transplant outcomes. 2 Disease type, recipient age, source of the stem cells, type of donor, conditioning regimen, use of serotherapy, prophylaxis and treatment for graft-versus-host disease (GvHD) and viral infections may have a major impact on IR.3–8 Despite numerous studies, predictive immune parameters of clinical outcomes remains elusive due to the variety of cut-off values for lymphocyte counts, time post-HSCT for samples collections, and the group of patients included in each study.4
There is a dearth of studies regarding IR after pediatric HSCT, especially for patients transplanted in resource-limited countries. In many places around the world, socioeconomic problems, availability of well-matched donors, lack of drugs and tests limit access to this curative procedure. These barriers culminate in a lower volume of HSCT, and consequently in lower number of publications on this topic compared with North America and Europe. 9
Our objective was to analyze the absolute lymphocyte count (ALC) and lymphocyte subpopulations after HSCT and correlate these factors with transplant characteristics and post-transplant endpoints, such as overall survival, acute GvHD (aGvHD), cytomegalovirus (CMV) infection, and death.