Tissue-resident macrophages self-maintain locally throughout adult life with minimal contribution from circulating monocytes.

Despite accumulating evidence suggesting local self-maintenance of tissue macrophages in the steady state, the dogma remains that tissue macrophages derive from monocytes. Using parabiosis and fate-mapping approaches, we confirmed that monocytes do not show significant contribution to tissue macrophages in the steady state. Similarly, we found that after depletion of lung macrophages, the majority of repopulation occurred by stochastic cellular proliferation in situ in a macrophage colony-stimulating factor (M-Csf)- and granulocyte macrophage (GM)-CSF-dependent manner but independently of interleukin-4. We also found that after bone marrow transplantation, host macrophages retained the capacity to expand when the development of donor macrophages was compromised. Expansion of host macrophages was functional and prevented the development of alveolar proteinosis in mice transplanted with GM-Csf-receptor-deficient progenitors. Collectively, these results indicate that tissue-resident macrophages and circulating monocytes should be classified as mononuclear phagocyte lineages that are independently maintained in the steady state.

[Acquired hemophilia A: clinical and biological characteristics and therapeutic management of a series of eight patients hospitalized in Lariboisière and Saint-Louis hospitals]. / Hémophilie A acquise : caractéristiques clinico-biologiques et prise en charge thérapeutique d'une série de huit patients hospitalisés à Lariboisière et Saint-Louis.

Acquired hemophilia A is a rare autoimmune disease, linked to the appearance of autoantibodies directed against circulating factor VIII, and characterized by a major hemorrhagic syndrome. Acquired hemophilia A is a life-threatening diagnostic and therapeutic medical emergency. We describe here the cohort of patients with acquired hemophilia A treated between 2015 and 2020 at Lariboisière and Saint-Louis University Hospitals (Paris, France). We remind you here of the measures to be taken without delay in the face of any clinical and/or biological suspicion. Management is based on three main areas published in multicentre cohort studies, essentially observational: symptomatic treatment to control the hemorrhagic syndrome, immunosuppressive treatment to eradicate autoantibodies and manage their possible complications, and etiological treatment of the underlying pathology for secondary forms.

[Lupus anticoagulant and ischemic strokes: about two case reports]. / Anticoagulant lupique et accidents vasculaires cérébraux ischémiques : à propos de deux observations.

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by thrombotic clinical manifestations, including ischemic stroke. Testing for lupus anticoagulant (LA) among antiphospholipid antibodies is key to the diagnosis of antiphospholipid syndrome (APS). Given the impact on patient management, close clinician-pathologist collaboration is crucial for the presence of LA in a thrombotic setting. Testing for LA must be carried out using specific and appropriate clotting assays and the pathologist should be aware of interferences. We report here two cases of stroke associated with the presence of LA, and recall the strategy for screening for LA.

Intestinal goblet cells protect against GVHD after allogeneic stem cell transplantation via Lypd8.

Graft-versus-host disease (GVHD) and infection are major obstacles to successful allogeneic hematopoietic stem cell transplantation (HSCT). Intestinal goblet cells form the mucus layers, which spatially segregate gut microbiota from host tissues. Although it is well known that goblet cell loss is one of the histologic features of GVHD, effects of their loss in pathophysiology of GVHD remain to be elucidated. In mouse models of allogeneic HSCT, goblet cells in the colon were significantly reduced, resulting in disruption of the inner mucus layer of the colon and increased bacterial translocation into colonic mucosa. Pretransplant administration of interleukin-25 (IL-25), a growth factor for goblet cells, protected goblet cells against GVHD, prevented bacterial translocation, reduced plasma concentrations of interferon-γ (IFN-γ) and IL-6, and ameliorated GVHD. The protective role of IL-25 was dependent on Lypd8, an antimicrobial molecule produced by enterocytes in the colon that suppresses motility of flagellated bacteria. In clinical colon biopsies, low numbers of goblet cells were significantly associated with severe intestinal GVHD, increased transplant-related mortality, and poor survival after HSCT. Goblet cell loss is associated with poor transplant outcome, and administration of IL-25 represents an adjunct therapeutic strategy for GVHD by protecting goblet cells.

R-Spondin1 expands Paneth cells and prevents dysbiosis induced by graft-versus-host disease.

The intestinal microbial ecosystem is actively regulated by Paneth cell-derived antimicrobial peptides such as α-defensins. Various disorders, including graft-versus-host disease (GVHD), disrupt Paneth cell functions, resulting in unfavorably altered intestinal microbiota (dysbiosis), which further accelerates the underlying diseases. Current strategies to restore the gut ecosystem are bacteriotherapy such as fecal microbiota transplantation and probiotics, and no physiological approach has been developed so far. In this study, we demonstrate a novel approach to restore gut microbial ecology by Wnt agonist R-Spondin1 (R-Spo1) or recombinant α-defensin in mice. R-Spo1 stimulates intestinal stem cells to differentiate to Paneth cells and enhances luminal secretion of α-defensins. Administration of R-Spo1 or recombinant α-defensin prevents GVHD-mediated dysbiosis, thus representing a novel and physiological approach at modifying the gut ecosystem to restore intestinal homeostasis and host-microbiota cross talk toward therapeutic benefits.

Intra-cheek immunization as a novel vaccination route for therapeutic vaccines of head and neck squamous cell carcinomas using plasmo virus-like particles.

Despite current therapy, head and neck squamous cell carcinomas (HNSCCs) arising from various mucosal sites of the upper aero-digestive tract frequently relapse in a loco-regional manner and have a poor prognosis. Our objective was to validate an innovative mucosal route of vaccination using plasmo virus-like particles (pVLPs) in a pre-clinical orthotopic model of HNSCCs. For this purpose, we used pVLP-E7, that are plasmid DNA encoding retroviral virus-like particles carrying a truncated E7 oncoprotein from HPV-16 as antigen model, to vaccinate mice bearing pre-established TC-1 tumors implanted into the buccal mucosa. pVLP-E7 were combined with clinical grade TLR agonists (Imiquimod and CpG-ODN). In this pre-clinical orthotopic model, whose tumor microenvironment resembles to those of human HNSCCs, different mucosal vaccination routes were tested for their ability to elicit efficient immune and antitumoral responses. Results showed that mucosal intra-cheek (IC) vaccinations using pVLP-E7, comparatively to intradermic vaccinations (ID), gave rise to higher mobilization of mucosal (CD49a(+)) CD8(+) specific effector T cells in both tumor draining lymph nodes (TdLNs) and tumor microenvironment resulting in better antitumor effects and in a long-term protection against tumor rechallenge. In vivo CD8(+) depletion demonstrated that antitumoral effects were fully dependent upon the presence of CD8(+) T cells. Validation of IC mucosal vaccinations with pVLPs combined with adjuvants using a pre-clinical orthotopic model of HNSCC provides valuable pre-clinical data to rapidly envision the use of such therapeutic vaccines in patients with HNSCCs, inasmuch as vaccinal components and adjuvants can be easily obtained as clinical grade reagents.

CD169⁺ macrophages provide a niche promoting erythropoiesis under homeostasis and stress.

A role for macrophages in erythropoiesis was suggested several decades ago when erythroblastic islands in the bone marrow, composed of a central macrophage surrounded by developing erythroblasts, were described. However, the in vivo role of macrophages in erythropoiesis under homeostatic conditions or in disease remains unclear. We found that specific depletion of CD169(+) macrophages markedly reduced the number of erythroblasts in the bone marrow but did not result in overt anemia under homeostatic conditions, probably because of concomitant alterations in red blood cell clearance. However, CD169(+) macrophage depletion significantly impaired erythropoietic recovery from hemolytic anemia, acute blood loss and myeloablation. Furthermore, macrophage depletion normalized the erythroid compartment in a JAK2(V617F)-driven mouse model of polycythemia vera, suggesting that erythropoiesis in polycythemia vera remains under the control of macrophages in the bone marrow and splenic microenvironments. These results indicate that CD169(+) macrophages promote late erythroid maturation and that modulation of the macrophage compartment may be a new strategy to treat erythropoietic disorders.