Literature context: 30-F11) BioLegend Cat#103116; RRID:AB_312981 Anti-mouse CD45 FITC (clone I3/
Onset of cardiovascular complications as a consequence of atherosclerosis exhibits a circadian incidence with a peak in the morning hours. Although development of atherosclerosis extends for long periods of time through arterial leukocyte recruitment, we hypothesized that discrete diurnal invasion of the arterial wall could sustain atherogenic growth. Here, we show that myeloid cell recruitment to atherosclerotic lesions oscillates with a peak during the transition from the activity to the resting phase. This diurnal phenotype is regulated by rhythmic release of myeloid cell-derived CCL2, and blockade of its signaling abolished oscillatory leukocyte adhesion. In contrast, we show that myeloid cell adhesion to microvascular beds peaks during the early activity phase. Consequently, timed pharmacological CCR2 neutralization during the activity phase caused inhibition of atherosclerosis without disturbing microvascular recruitment. These findings demonstrate that chronic inflammation of large vessels feeds on rhythmic myeloid cell recruitment, and lay the foundation for chrono-pharmacology-based therapy.
Literature context: [30-F11] BioLegend Cat# 103116; RRID:AB_312981 Brilliant Violet 605 anti-mouse
The nervous system, the immune system, and microbial pathogens interact closely at barrier tissues. Here, we find that a bacterial pathogen, Streptococcus pyogenes, hijacks pain and neuronal regulation of the immune response to promote bacterial survival. Necrotizing fasciitis is a life-threatening soft tissue infection in which "pain is out of proportion" to early physical manifestations. We find that S. pyogenes, the leading cause of necrotizing fasciitis, secretes streptolysin S (SLS) to directly activate nociceptor neurons and produce pain during infection. Nociceptors, in turn, release the neuropeptide calcitonin gene-related peptide (CGRP) into infected tissues, which inhibits the recruitment of neutrophils and opsonophagocytic killing of S. pyogenes. Botulinum neurotoxin A and CGRP antagonism block neuron-mediated suppression of host defense, thereby preventing and treating S. pyogenes necrotizing infection. We conclude that targeting the peripheral nervous system and blocking neuro-immune communication is a promising strategy to treat highly invasive bacterial infections. VIDEO ABSTRACT.
Literature context: end Cat#103116; RRID:AB_312981 Anti-CD45.1 (clone A20) BioLege
CD4+ T cells orchestrate immune responses and destruction of allogeneic organ transplants, but how this process is regulated on a transcriptional level remains unclear. Here, we demonstrated that interferon regulatory factor 4 (IRF4) was a key transcriptional determinant controlling T cell responses during transplantation. IRF4 deletion in mice resulted in progressive establishment of CD4+ T cell dysfunction and long-term allograft survival. Mechanistically, IRF4 repressed PD-1, Helios, and other molecules associated with T cell dysfunction. In the absence of IRF4, chromatin accessibility and binding of Helios at PD-1 cis-regulatory elements were increased, resulting in enhanced PD-1 expression and CD4+ T cell dysfunction. The dysfunctional state of Irf4-deficient T cells was initially reversible by PD-1 ligand blockade, but it progressively developed into an irreversible state. Hence, IRF4 controls a core regulatory circuit of CD4+ T cell dysfunction, and targeting IRF4 represents a potential therapeutic strategy for achieving transplant acceptance.
Literature context: (rat monoclonal) BioLegend RRID:AB_312981 clone: 30-F11
How tissue-resident macrophages (TRM) impact adaptive immune responses remains poorly understood. We report novel mechanisms by which TRMs regulate T cell activities at tissue sites. These mechanisms are mediated by the complement receptor of immunoglobulin family (CRIg). Using animal models for autoimmune type 1 diabetes (T1D), we found that CRIg+ TRMs formed a protective barrier surrounding pancreatic islets. Genetic ablation of CRIg exacerbated islet inflammation and local T cell activation. CRIg exhibited a dual function of attenuating early T cell activation and promoting the differentiation of Foxp3+ regulatory (Treg) cells. More importantly, CRIg stabilized the expression of Foxp3 in Treg cells, by enhancing their responsiveness to interleukin-2. The expression of CRIg in TRMs was postnatally regulated by gut microbial signals and metabolites. Thus, environmental cues instruct TRMs to express CRIg, which functions as an immune checkpoint molecule to regulate adaptive immunity and promote immune tolerance.
Literature context: PC-Cy7 Biolegend Cat#103116; RRID:AB_312981 Anti-mouse CD45 clone 30-F11, P
Alveolar macrophages (AMs) derive from fetal liver monocytes, which colonize the lung during embryonic development and give rise to fully mature AMs perinatally. AM differentiation requires granulocyte macrophage colony-stimulating factor (GM-CSF), but whether additional factors are involved in AM regulation is not known. Here we report that AMs, in contrast to most other tissue macrophages, were also dependent on transforming growth factor-β receptor (TGF-βR) signaling. Conditional deletion of TGF-βR in mice at different time points halted the development and differentiation of AMs. In adult mice, TGF-β was also critical for AM homeostasis. The source of TGF-β was AMs themselves, indicative of an autocrine loop that promotes AM self-maintenance. Mechanistically, TGF-βR signaling resulted in upregulation of PPAR-γ, a signature transcription factor essential for the development of AMs. These findings reveal an additional layer of complexity regarding the guidance cues, which govern the genesis, maturation, and survival of AMs.
Literature context: t#103116; RRID:AB_312981 Rat monocl
To investigate the role of immune cells in lung regeneration, we used a unilateral pneumonectomy model that promotes the formation of new alveoli in the remaining lobes. Immunofluorescence and single-cell RNA sequencing found CD115+ and CCR2+ monocytes and M2-like macrophages accumulating in the lung during the peak of type 2 alveolar epithelial stem cell (AEC2) proliferation. Genetic loss of function in mice and adoptive transfer studies revealed that bone marrow-derived macrophages (BMDMs) traffic to the lung through a CCL2-CCR2 chemokine axis and are required for optimal lung regeneration, along with Il4ra-expressing leukocytes. Our data suggest that these cells modulate AEC2 proliferation and differentiation. Finally, we provide evidence that group 2 innate lymphoid cells are a source of IL-13, which promotes lung regeneration. Together, our data highlight the potential for immunomodulatory therapies to stimulate alveologenesis in adults.
Literature context: t#103116; RRID:AB_312981 Rat monocl
Lambda interferons (IFNλs) or type III IFNs share homology, expression patterns, signaling cascades, and antiviral functions with type I IFNs. This has complicated the unwinding of their unique non-redundant roles. Through the systematic study of influenza virus infection in mice, we herein show that IFNλs are the first IFNs produced that act at the epithelial barrier to suppress initial viral spread without activating inflammation. If infection progresses, type I IFNs come into play to enhance viral resistance and induce pro-inflammatory responses essential for confronting infection but causing immunopathology. Central to this are neutrophils which respond to both cytokines to upregulate antimicrobial functions but exhibit pro-inflammatory activation only to type I IFNs. Accordingly, Ifnlr1-/- mice display enhanced type I IFN production, neutrophilia, lung injury, and lethality, while therapeutic administration of PEG-IFNλ potently suppresses these effects. IFNλs therefore constitute the front line of antiviral defense in the lung without compromising host fitness.
Literature context: d 103116; RRID:AB_312981 FITC-conju
Idiopathic pulmonary fibrosis (IPF) is a form of progressive interstitial lung disease with unknown etiology. Due to a lack of effective treatment, IPF is associated with a high mortality rate. The hallmark feature of this disease is the accumulation of activated myofibroblasts that excessively deposit extracellular matrix proteins, thus compromising lung architecture and function and hindering gas exchange. Here we investigated the origin of activated myofibroblasts and the molecular mechanisms governing fibrosis formation and resolution. Genetic engineering in mice enables the time-controlled labeling and monitoring of lipogenic or myogenic populations of lung fibroblasts during fibrosis formation and resolution. Our data demonstrate a lipogenic-to-myogenic switch in fibroblastic phenotype during fibrosis formation. Conversely, we observed a myogenic-to-lipogenic switch during fibrosis resolution. Analysis of human lung tissues and primary human lung fibroblasts indicates that this fate switching is involved in IPF pathogenesis, opening potential therapeutic avenues to treat patients.