Pancreatic islet transplantation (PITx) is a promising treatment option for patients with type 1 diabetes mellitus. Previously, we demonstrated that therapy with alloantigen-specific immunomodulatory cells (IMCs) generated ex vivo in the presence of anti-CD80 and CD86 monoclonal antibodies (mAbs), successfully induced tolerance following clinical liver transplantation. To extend IMC therapy to PITx, it is crucial to address the strong inflammatory and innate immune responses that occur immediately after PITx. In this study, we investigated the efficacy of IMCs in modulating macrophage activation and mitigating inflammatory damage of pancreatic islets. IMCs were induced using mouse splenocytes in the presence of anti-mouse anti-CD80 (RM80) and anti-CD86 (GL-1) mAbs. IMCs exerted donor-specific immunosuppressive effects in a mixed lymphocyte reaction. During lipopolysaccharide (LPS) stimulation, the addition of IMCs suppressed conversion to the M1 phenotype and promoted a shift toward the M2 phenotype, particularly under direct cell-cell contact conditions. Nitric oxide production, a hallmark of M1 polarized macrophages, was significantly reduced in LPS-stimulated RAW264 macrophages by IMC treatment. These findings were associated with reduced secretion of pro-inflammatory cytokines, tumoral necrosis factor α, and interleukin-6, and increased interleukin-10 production by macrophages. IMCs effectively prevented macrophage-mediated islet destruction after 12 h of co-culture with LPS-stimulated macrophages and significantly inhibited macrophage migration toward allogeneic islets in vitro. Intraportal co-infusion of IMCs with syngeneic islets in a mouse PITx model resulted in reduced messenger RNA (mRNA) expression of pro-inflammatory cytokines in the recipient liver. Immunohistochemical staining revealed a significantly lower number of F4/80+ macrophages at the transplantation site in IMCs-treated mice. These results demonstrate that IMCs modulate macrophage polarization, promoting a shift toward the M2 phenotype and protecting islets from macrophage-mediated damage. These effects combined with its intrinsic donor antigen-specific immunosuppressive capacity make IMC therapy a promising strategy for improving outcomes after PITx.

Endothelial cells are integral components of all vasculature within complex organisms. As they line the blood vessel wall, endothelial cells are constantly exposed to a variety of molecular factors and shear force that can induce cellular damage and stress. However, how endothelial cells are removed or eliminate unwanted cellular contents, remains unclear. The generation of large extracellular vesicles (EVs) has emerged as a key mechanism for the removal of cellular waste from cells that are dying or stressed. Here, we used intravital microscopy of the bone marrow to directly measure the kinetics of EV formation from endothelial cells in vivo under homoeostatic and malignant conditions. These large EVs are mitochondria-rich, expose the 'eat me' signal phosphatidylserine, and can interact with immune cell populations as a potential clearance mechanism. Elevated levels of circulating EVs correlates with degradation of the bone marrow vasculature caused by acute myeloid leukaemia. Together, our study provides in vivo spatio-temporal characterization of EV formation in the murine vasculature and suggests that circulating, large endothelial cell-derived EVs can provide a snapshot of vascular damage at distal sites.
© 2024. The Author(s).

Cryptococcosis is a neglected fungal disease that causes many deaths annually, is primarily caused by Cryptococcus neoformans and Cryptococcus gattii species. They are environmental fungus that engages lung pneumonia and a severe systemic infection. The rising incidence of affected immunocompetent hosts, particularly by the aggressive Cryptococcus deuterogattii (R265), underscores the urgency to understand factors influencing its dissemination. The immunopathogenesis of R265 infection is incompletely understood. Therefore, we investigate the role of IL-22 and IL-23 cytokines during R265 cryptocococcosis. Our findings highlight the crucial role of IL-22 and IL-23 cytokines in lung barrier homeostasis, preventing excessive lung damage. IL-22 not only prevents neutrophil infiltration and IL-17A production but also facilitates eosinophil lung infiltration. Ultimately, this study contributes vital insights into the selective role of IL-22 and IL-23 cytokines in immune activation and tissue regulation during the aggressive R265 lung and systemic infection.
© 2024 The Author(s).

Mast cells (MCs) are tissue-resident immune cells that exhibit homeostatic and neuron-associated functions. Here, we combined whole-tissue imaging and single-cell RNA sequencing datasets to generate a pan-organ analysis of MCs in mice and humans at steady state. In mice, we identify two mutually exclusive MC populations, MrgprB2+ connective tissue-type MCs and MrgprB2neg mucosal-type MCs, with specific transcriptomic core signatures. While MrgprB2+ MCs develop in utero independently of the bone marrow, MrgprB2neg MCs develop after birth and are renewed by bone marrow progenitors. In humans, we unbiasedly identify seven MC subsets (MC1-7) distributed across 12 organs with different transcriptomic core signatures. MC1 are preferentially enriched in the bladder, MC2 in the lungs, and MC4, MC6, and MC7 in the skin. Conversely, MC3 and MC5 are shared by most organs but not skin. This comprehensive analysis offers valuable insights into the natural diversity of MC subtypes in both mice and humans.
© 2023 Tauber et al.

Innate lymphoid cells (ILCs) and adaptive T cells remain a challenge to study because of a significant overlap in their transcriptomic profiles. Here, we describe the adoptive transfer of ILC progenitors into mice genetically deficient in innate and adaptive immune cells to allow detailed study of the development and function of ILCs and gene regulation in an in vivo setting. For complete details on the use and execution of this protocol, please refer to Jacquelot et al. (2021) and Seillet et al. (2016).
Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.