Dendritic cells in allogeneic hematopoietic stem cell transplantation

Child with Wiskott–Aldrich syndrome underwent atypical immune reconstruction after umbilical cord blood transplantation: A case report

BACKGROUND

Timely reconstitution of a donor-derived immune system is important for recovery and long-term survival of patients after allogeneic hematopoietic stem cell transplantation (HSCT). We describe a case of Wiskott–Aldrich syndrome (WAS) treated by umbilical cord blood transplantation (UCBT) with atypical immune reconstruction.

CASE SUMMARY

A 1-year-old Chinese male infant was diagnosed with WAS. WAS gene sequencing identified the mutation c.777 + 1G>A (IVS8). On August 8, 2017, he was admitted to our hospital for HSCT. We selected an unrelated Human leukocyte antigen 6/10-matched donor for UCBT. After HSCT, the immune reconstitution process was atypical, the lymphocytes reached 0.5 × 10⁹/L on day 23, and the neutrophils reached 0.5 × 10⁹/L on day 34. The patient’s recovery throughout the year was good.

CONCLUSION

An increase in lymphocytes (especially T cells) earlier than granulocytes may be a marker of a good prognosis in UCBT.

CD56bright natural killer regulatory cells in filgrastim primed donor blood or marrow products regulate chronic graft-versus-host disease: the Canadian Blood and Marrow Transplant Group randomized 0601 study results

Randomized trials have conclusively shown higher rates of chronic graft-versus-host disease with filgrastim-stimulated apheresis peripheral blood as a donor source than unstimulated bone marrow. The Canadian Blood and Marrow Transplant Group conducted a phase 3 study of adults who received either filgrastim-stimulated apheresis peripheral blood or filgrastim-stimulated bone marrow from human leukocyte antigen-identical sibling donors. Because all donors received the identical filgrastim dosing schedule, this study allowed for a controlled evaluation of the impact of stem cell source on development of chronic graft-versus-host disease. One hundred and twenty-one evaluable filgrastim-stimulated apheresis peripheral blood and filgrastim-stimulated bone marrow patient donor products were immunologically characterized by flow cytometry and tested for their association with acute and chronic graft-versus-host disease within 2 years of transplantation. The immune populations evaluated included, regulatory T cells, central memory and effector T cells, interferon γ positive producing T cells, invariate natural killer T cells, regulatory natural killer cells, dendritic cell populations, macrophages, and activated B cells and memory B cells. When both filgrastim-stimulated apheresis peripheral blood and filgrastim-stimulated bone marrow were grouped together, a higher chronic graft-versus-host disease frequency was associated with lower proportions of CD56^bright natural killer regulatory cells and interferon γ-producing T helper cells in the donor product. Lower CD56^bright natural killer regulatory cells displayed differential impacts on the development of extensive chronic graft-versus-host disease between filgrastim-stimulated apheresis peripheral blood and filgrastim-stimulated bone marrow. In summary, while controlling for the potential impact of filgrastim on marrow, our studies demonstrated that CD56^bright natural killer regulatory cells had a much stronger impact on filgrastim-stimulated apheresis peripheral blood than on filgrastim-stimulated bone marrow. This supports the conclusion that a lower proportion of CD56^bright natural killer regulatory cells results in the high rate of chronic graft-versus-host disease seen in filgrastim-stimulated apheresis peripheral blood. clinicaltrials.gov Identifier: 00438958.

Homeostatic cytokines in immune reconstitution and graft-versus-host disease

For numerous patients, allogeneic stem cell transplantation (SCT) is the only therapeutic option that could potentially cure their disease. Despite significant progress made in clinical management of allogeneic SCT, acute graft-versus-host disease (aGVHD) remains the second cause of death after disease recurrence. aGVHD is highly immunosuppressive and the adverse effect of allogeneic SCT on T cell regeneration is typically more important than the levels of immunosuppression normally seen after autologous SCT. In these patients, immune reconstitution often takes several years to occur and restoring immunocompetence after allogeneic SCT represents an important challenge, principally because clinical options are limited and current methods used to accelerate immune reconstitution are associated with increased GVHD. Interleukin-7 and IL-15 are both under clinical investigation and demonstrate the greatest potential on peripheral T cells regeneration in mice and humans. However, awareness has been raised about the use of IL-7 and IL-15 after allogeneic SCT with regards to potential adverse effects on aGVHD. In this review, we will discuss about recent progress made in lymphocyte regeneration, the critical role played by IL-7 and IL-15 in T cell homeostasis and how these cytokines could be used to improve immune reconstitution after allogeneic SCT.

Dendritic cell reconstitution is associated with relapse-free survival and acute GVHD severity in children after allogeneic stem cell transplantation

DCs are potent APCs and key regulators of innate and adaptive immunity. After allo-SCT, their reconstitution in the peripheral blood (PB) to levels similar to those in healthy individuals tends to be slow. We investigate the age- and sex-dependant immune reconstitution of myeloid (mDC) and plasmacytoid DC (pDC) in the PB of 45 children with leukaemia or myelodysplastic syndrome (aged 1-17 years, median 10) after allo-SCT with regard to relapse, acute GVHD (aGVHD) and relapse-free survival. Low pDC/μL PB up to day 60 post SCT are associated with higher incidence of moderate or severe aGVHD (P=0.035), whereas high pDC/μL PB up to day 60 are associated with higher risk of relapse (P<0.001). The time-trend of DCs/μL PB for days 0-200 is a significant predictor of relapse-free survival for both mDCs (P<0.001) and pDCs (P=0.020). Jointly modelling DC reconstitution and complications improves on these simple criteria. Compared with BM, PBSC transplants tend to show slower mDC/pDC reconstitution (P=0.001, 0.031, respectively), but have no direct effect on relapse-free survival. These results suggest an important role for both mDCs and pDCs in the reconstituting immune system. The inclusion of mDCs and pDCs may improve existing models for complication prediction following allo-SCT.

HDAC inhibition and graft versus host disease

Histone deacetylase (HDAC) inhibitors are currently used clinically as anticancer drugs. Recent data have demonstrated that some of these drugs have potent antiinflammatory or immunomodulatory effects at noncytotoxic doses. The immunomodulatory effects have shown potential for therapeutic benefit after allogeneic bone marrow transplantation in several experimental models of graft versus host disease (GVHD). These effects, at least in part, result from the ability of HDAC inhibitors (HDACi) to suppress the function of host antigen presenting cells such as dendritic cells (DC). HDACi reduce the dendritic cell (DC) responses, in part, by enhancing the expression of indoleamine 2,3-dioxygenase (IDO) in a signal transducer and activator of transcription-3 (STAT-3) dependent manner. They also alter the function of other immune cells such as T regulatory cells and natural killer (NK) cells, which also play important roles in the biology of GVHD. Based on these observations, a clinical trial has been launched to evaluate the impact of HDAC inhibitors on clinical GVHD. The experimental, mechanistic studies along with the brief preliminary observations from the ongoing clinical trial are discussed in this review.

Differential gene expression signatures of adult peripheral blood vs cord blood monocyte-derived immature and mature dendritic cells

OBJECTIVE

Our previous studies have demonstrated differentially expressed genetic signature patterns in adult peripheral blood (APB) monocytes (Mos) vs cord blood (CB) Mos.

MATERIALS AND METHODS

In this study, we examined the differential gene expression profiles of APB vs CB immature dendritic cells (iDCs) and mature dendritic cells (mDCs) derived from Mos.

RESULTS

By utilizing oligonucleotide microarray, significant differential gene expression signature patterns were identified in APB vs CB mDCs, including increased expression of chemokines, cytokine receptors, and cell surface molecules. Additionally, signaling protein genes were significantly overexpressed in APB vs CB mDCs. There was also a significant amplification of expression of transcription factor interferon (IFN) regulatory factors and structure regulatory genes in APB vs CB mDCs. In contrast, there were genes expressed significantly higher in CB vs APB mDCs, including cell-cycle regulators and signaling molecule gene.

CONCLUSION

Taken together, these results suggest that specific genetic signatures might be responsible for differential DC differentiation and maturation between APB vs CB, and may provide insight into molecular mechanisms regulating differential immune responses between neonates and adults.

Frontiers of immunological tolerance

Herein, we succinctly review mechanisms underlying self-tolerance and the roles of dendritic leukocytes (DCs) in T-cell tolerance to self and foreign antigens. We also consider the properties of naturally arising and other populations of regulatory T cells (Treg), together with growing evidence that interplay between DCs and Treg cells can sustain antigen-specific tolerance. B-cell tolerance and the role of hematopoietic cell chimerism in the induction and maintenance of tolerance are also discussed, as is the impact of cosignaling pathway manipulation on tolerance induction. This overview also surveys prospects for technological advances in the monitoring and prediction of tolerance and the application of genomic and proteomic analysis. In addition, we consider potential novel therapeutic targets for promotion of tolerance induction.

Physiologic regulation of central and peripheral T cell tolerance: lessons for therapeutic applications

Immunologic tolerance is a state of unresponsiveness that is specific for a particular antigen. The immune system has an extraordinary potential for making T cell and B cell that recognize and neutralize any chemical entity and microbe entering the body. Certainly, some of these T cells and B cells recognize self-components; therefore, cellular mechanisms have evolved to control the activity of these self-reactive cells and achieve immunological self-tolerance. The most important in vivo biological significance of mechanisms regulating self-tolerance is to prevent the immune system from mounting an attack against the host's own tissues resulting in autoimmunity. This review summarizes recent developments in our understanding of T-helper cell tolerance and discusses how the new findings can be exploited to prevent and treat autoimmune diseases, allergy, cancer, and chronic infection, or establish donor-specific transplantation tolerance.

Biological response modifiers as adjuncts to stem cell transplantation

Cytokines produced by immune and non-immune cells serve as potent mediators with the properties of signal cells that coordinate the immune response. They are delivered by cells either to the systemic circulation or to the local environment. They are being used at present in the field of stem cell transplantation (SCT) in order to improve transplant outcome. This paper reviews the existing data on pre-, peri- and post-SCT treatment with cytokines.