Talmadge J.E.Singh R.Ino K.Ageitos A.Buyukberber S.2024-08-042024-08-0420000192-0561https://doi.org/10.1016/S0192-0561(00)00078-3https://hdl.handle.net/11616/90529High dose therapy (HDT) and stem cell transplantation (SCT) results in alterations in the immunologic network, thymic re-education and the induction of peripheral tolerance. The changes to the immunoregulatory cascade and tolerance induction associated with autotransplants have been investigated in a series of studies focused on leukocyte reconstitution and function following HDT and autologous SCT. In these studies, we observed a significant decrease in the CD4:CD8 T cell ratio post-transplantation compared to normal peripheral blood (PB) donors due to a decrease in CD4+ cells. In addition, T cell function (phytohemagglutinin (PHA) mitogenesis) was consistently depressed compared to samples obtained from normal PB donors. The loss of T cell function was associated with an increased frequency of circulating monocytes, their expression of Fas ligand (FasL) and a high frequency of apoptotic CD4+ T cells. Indeed, 28-51% of circulating CD4+ T cells were observed to be apoptotic during the first 100 days following HDT and SCT. These studies suggest that 'primed' or activated Fas+ CD4+ lymphocytes interact with FasL+ monocytes, resulting in apoptosis, leading to the preferential deletion of CD4+ T cells, a decrease in the CD4:CD8 T cell ratio and depressed T cell function. Further, as discussed herein, the T cells are activated with a predominantly type 2 phenotype, which may also contribute to the maintenance of the immunosuppressive condition. Therefore, there is the potential to regulate immune recovery by stem cell product manipulation or post-transplantation cytokine administration. © 2000 International Society for Immunopharmacology.eninfo:eu-repo/semantics/closedAccessImmune regulationPeripheral toleranceT cell functionArticle2212104110561113761110.1016/S0192-0561(00)00078-32-s2.0-0034537473N/A