Curative islet and hematopoietic cell transplantation in diabetic mice without toxic bone marrow conditioning

Slow cycling and durable Flt3+ progenitors contribute to hematopoiesis under native conditions

The dynamics of the hematopoietic flux responsible for blood cell production in native conditions remains a matter of debate. Using CITE-seq analyses, we uncovered a distinct progenitor population that displays a cell cycle gene signature similar to the one found in quiescent hematopoietic stem cells. We further determined that the CD62L marker can be used to phenotypically enrich this population in the Flt3+ multipotent progenitor (MPP4) compartment. Functional in vitro and in vivo analyses validated the heterogeneity of the MPP4 compartment and established the quiescent/slow-cycling properties of the CD62L- MPP4 cells. Furthermore, studies under native conditions revealed a novel hierarchical organization of the MPP compartments in which quiescent/slow-cycling MPP4 cells sustain a prolonged hematopoietic activity at steady-state while giving rise to other lineage-biased MPP populations. Altogether, our data characterize a durable and productive quiescent/slow-cycling hematopoietic intermediary within the MPP4 compartment and highlight early paths of progenitor differentiation during unperturbed hematopoiesis.

Adoptive transfer of allergen-expressing B cells prevents IgE-mediated allergy

Introduction

Prophylactic strategies to prevent the development of allergies by establishing tolerance remain an unmet medical need. We previously reported that the transfer of autologous hematopoietic stem cells (HSC) expressing the major timothy grass pollen allergen, Phl p 5, on their cell surface induced allergen-specific tolerance in mice. In this study, we investigated the ability of allergen-expressing immune cells (dendritic cells, CD4+ T cells, CD8+ T cells, and CD19+ B cells) to induce allergen-specific tolerance in naive mice and identified CD19+ B cells as promising candidates for allergen-specific cell therapy.

Methods

For this purpose, CD19+ B cells were isolated from Phl p 5-transgenic BALB/c mice and transferred to naive BALB/c mice, pre-treated with a short course of rapamycin and an anti-CD40L antibody. Subsequently, the mice were subcutaneously sensitized three times at 4-week intervals to Phl p 5 and Bet v 1 as an unrelated control allergen. Allergen-expressing cells were followed in the blood to monitor molecular chimerism, and sera were analyzed for Phl p 5- and Bet v 1-specific IgE and IgG1 levels by RBL assay and ELISA, respectively. In vivo allergen-induced lung inflammation was measured by whole-body plethysmography, and mast cell degranulation was determined by skin testing.

Results

The transfer of purified Phl p 5-expressing CD19+ B cells to naive BALB/c mice induced B cell chimerism for up to three months and prevented the development of Phl p 5-specific IgE and IgG1 antibody responses for a follow-up period of 26 weeks. Since Bet v 1 but not Phl p 5-specific antibodies were detected, the induction of tolerance was specific for Phl p 5. Whole-body plethysmography revealed preserved lung function in CD19+ B cell-treated mice in contrast to sensitized mice, and there was no Phl p 5-induced mast cell degranulation in treated mice.

Discussion

Thus, we demonstrated that the transfer of Phl p 5-expressing CD19+ B cells induces allergen-specific tolerance in a mouse model of grass pollen allergy. This approach could be further translated into a prophylactic regimen for the prevention of IgE-mediated allergy in humans.

Advances in dendritic cell targeting nano-delivery systems for induction of immune tolerance

Dendritic cells (DCs) are the major specialized antigen-presenting cells (APCs), play a key role in initiating the body's immune response, maintain the balance of immunity. DCs can also induce immune tolerance by rendering effector T cells absent and anergy, and promoting the expansion of regulatory T cells. Induction of tolerogenic DCs has been proved to be a promising strategy for the treatment of autoimmune diseases, organ transplantation, and allergic diseases by various laboratory researches and clinical trials. The development of nano-delivery systems has led to advances in situ modulation of the tolerance phenotype of DCs. By changing the material composition, particle size, zeta-potential, and surface modification of nanoparticles, nanoparticles can be used for the therapeutic payloads targeted delivery to DCs, endowing them with great potential in the induction of immune tolerance. This paper reviews how nano-delivery systems can be modulated for targeted delivery to DCs and induce immune tolerance and reviews their potential in the treatment of autoimmune diseases, organ transplantation, and allergic diseases.

Bone marrow chimerism breaks the barrier to pancreatic islet transplantation

In their recent Cell Reports paper, Chang and colleagues report on a successful strategy to achieve durable mixed hematopoietic chimerism that promotes the engraftment and long-term function of pancreatic islet allotransplants in fully immunocompetent mice without immunosuppression.