Evaluation of lymphoid T immune recovery after hematopoietic stem cell transplant in patients with previous diagnosis of acute leukemia or myelodysplastic syndrome

Abstract

Hematopoietic stem cell transplantation (HSCT) is a procedure against a variety of neoplastic or immunological diseases, and it has as its primary purpose the restoration of hematopoietic and immune systems. The discovery of the gene region "major histocompatibility complex" was extremely important for HSCT to actually become a viable therapy in humans because it is through this region that are encoded proteins which are expressed on the cell surface and where it will be able to differentiate self antigens from non-self antigens, a basic and essential mechanism directly related to the rejection process of or graft's tolerance. The immune system's recovery occurs gradually after HSCT, more accurately, the recovery of T lymphoid compartment requires that T lymphoid precursors in bone marrow migrate to thymus and there undergo a process of maturation and differentiation such so that lymphocytes released to circulation are able to act in different immune responses like rejection and/or tolerance throughout the individual's life. However, during the immune system's recovery, there is a high risk for infections' development and graft-versus-host disease (GVHD). In order to decrease the infections' exposition and to increase the control of GVHD, it must be an adequate homeostatic balance between the different lymphocytes' subpopulations (regulatory T cells versus effector T cells) as well as effective differentiation and maturation of T lymphocytes during their pathway into the thymus. Based on these concepts, the main goal of the present study is to evaluate the post-HSCT lymphoid recovery of patients with prior diagnosis of acute leukemia or myelodysplastic syndrome and to compare it with the emergence of GVHD and infections. Thus, it will contribute to a better insight about the mechanisms which are involved in the interaction between rejection and tolerance and about body's capacity to support different types of infections. (AU)