Interleukin-2: a double-edge sword in allogeneic stem cell transplantation

Intermittent Exposure of Hypercapnia Suppresses Allograft Rejection via Induction of Treg Differentiation and Inhibition of Neutrophil Accumulation

Background: In the management of major burn wounds, allogeneic skin transplantation is a critical procedure to improve wound repair. Our previous works found that intermittent exposure to carbon dioxide leads to permissive hypercapnia (HCA) and prolongs skin allograft survival. However, the modulatory effects of HCA exposure on the immune system are not well understood. Objectives: Our purpose was to investigate how intermittent exposure to HCA can effectively reduce the immune reaction to allogeneic skin graft rejection. Methods: A fully major histocompatibility complex-incompatible skin transplant from BALB/c to C57BL/6 mice model was utilized. Immune cells from splenic and draining lymph nodes were analyzed by flow cytometry. Serum proinflammatory cytokines were analyzed by ELISA. Results: Serum levels of IFN-γ, IL-2, IL-6, and TNF-α were significantly decreased in the HCA group. Additionally, the percentage of CD8+ cells in draining lymph nodes was significantly lower in HCA than in the control group. Moreover, the generation rate of FoxP3+ regulatory T cells (Tregs) from spleen naïve CD4+ T cells was increased by intermittent exposure to carbon dioxide. The infiltrated neutrophils were also eliminated by HCA. Taken together, we concluded that intermittent hypercapnia exposure could effectively suppress skin rejection by stimulating Treg cell generation and suppressing immune reactions.

Prediction, management, and prognosis of mixed chimerism after hematopoietic stem cell transplantation in transfusion-dependent pediatric thalassemia patients

BACKGROUND

Early-onset mixed chimerism (MC) with a high proportion of residual host cells is considered a signal of graft rejection in patients undergoing allogenic hematopoietic stem cell transplantation for transfusion-dependent thalassemia. In order to prevent graft rejection and minimize the risk of treatment-related graft-versus-host disease (GVHD), we established a hierarchical management system based on chimerism analysis.

METHOD

This retrospective study provides a comprehensive review of the characteristics, interventions, and outcomes of the 38 patients who developed MC after transplantation among the 144 pediatric thalassemia patients between July 2007 and January 2019 at our center.

RESULTS

A sibling donor, a blood type-matched donor, conditioning regimens without fludarabine, and transplants containing <10 × 10⁸ total nucleated cells/kg were identified to be associated with the development of MC. Among the 38 patients developing MC, only four patients rejected the grafts. The response rate to donor lymphocyte infusion (DLI, only for patients receiving sibling donor transplantation) and cytokine immunomodulation without DLI was 70.6% and 42.9%, respectively. Patients that developed GVHD after DLI or cytokine therapy had a more significant increase in donor cell chimerism (16%, range 0%-35%) than those without (8.5%, range -21% to 40%, P = .049). However, even when treatment-related GVHD was included, patients with MC had a lower cumulative incidence of total acute GVHD than patients with complete donor chimerism (29.2% vs 48.0%, P = .030).

CONCLUSIONS

Interventions based on chimerism analysis were effective in preventing graft rejection and did not increase treatment-related GVHD in thalassemia patients with MC.

Delayed allogeneic skin graft rejection in CD26-deficient mice

Organ transplantation is an effective therapeutic tool for treating many terminal diseases. However, one of the biggest challenges of transplantation is determining how to achieve the long-term survival of the allogeneic or xenogeneic transplant by, for example, preventing transplant rejection. In the current study, CD26 gene-knockout mice were used to investigate the potential role of CD26/dipeptidyl peptidase-4 (DPPIV) in allogeneic skin graft rejection by tail-skin transplantation. Compared with wild-type (CD26^+/+) counterparts, CD26^-/- mice showed reduced necrosis of grafts and delayed graft rejection after skin transplantation. Concentrations of serum IgG, including its subclasses IgG1 and IgG2a, were significantly reduced in CD26^-/- mice during graft rejection. Moreover, after allogeneic skin transplantation, the secretion levels of the cytokines IFN-γ, IL-2, IL-6, IL-4, and IL-13 were significantly reduced, whereas the level of the cytokine IL-10 was increased in the serum of CD26^-/- mice compared with that in the serum of CD26^+/+ mice. Additionally, the concentration of IL-17 in serum and the percentage of cells secreting IL-17 in mouse peripheral blood lymphocytes (MPBLs) were both significantly lower, while the percentage of regulatory T cells (Tregs) was significantly higher in MPBLs of CD26^-/- mice than in those of CD26^+/+ mice. Furthermore, a lower percentage of CD8⁺ T cells in MPBLs and fewer infiltrated macrophages and T cells in graft tissues of CD26^-/- mice were detected during graft rejection. These results indicate that CD26 is involved in allogeneic skin graft rejection and provides another hint that CD26 deficiency leads to less rejection due to lower activation and proliferation of host immune cells.