Biology subjects

Davidson, D. J.

Publications and source records attributed to Davidson, D. J..

6 recordsLinked to original sources

bioRxiv2024

Proteomic analysis reveals dysregulation of peripheral blood neutrophils in patients with Multiple Sclerosis

Multiple Sclerosis (MS) is a complex auto-inflammatory disease affecting the brain and spinal cord, which results in axonal de-myelination and symptoms including fatigue, pain, and difficulties with vision and mobility. The involvement of the immune system in the pathology of MS is well established, particularly the adaptive T cell response, and there has been a particular focus on the IL-17-producing subset of Th17 cells and their role in driving disease. However, the importance of innate immune cells has not been so well characterised. Here we focused on neutrophils, which are innate immune cells and rapid responders to inflammation, and which have recently been linked to other chronic autoimmune conditions. Multiple strands of evidence in patients with MS and in mice with the experimental autoimmune encephalomyelitis MS model suggest neutrophils may play a role in driving MS inflammation. Here, we performed proteomic analysis on neutrophils from patients with MS and healthy donors, revealing striking differences. In particular, granule proteins were significantly more abundant in the MS neutrophils compared to the healthy controls, with a particular over-abundance of proteins in primary and secondary granules. In addition, members of the MAVS signalling pathway were differently regulated compared to healthy donor cells. Finally, we find that MS neutrophils do not suppress T cell activation equivalently to healthy neutrophils, and in particular are unable to suppress expression of CD161 on the T cells, indicative of Th17 differentiation. We propose that neutrophil dysregulation in MS may contribute to dysfunctional T cell responses.

immunology↗

bioRxiv2022

The antimicrobial peptide cathelicidin is critical for the development of Th17 responses in severe inflammatory disease

Multiple Sclerosis (MS) is a highly prevalent demyelinating autoimmune condition; the mechanisms regulating its severity and progression are unclear. The IL-17-producing Th17 subset of T cells has been widely implicated in MS and in the mouse model, experimental autoimmune encephalomyelitis (EAE). However, the differentiation and regulation of Th17 cells during EAE remain incompletely understood. Although evidence is mounting that the antimicrobial peptide cathelicidin profoundly affects early T cell differentiation, no studies have looked at its role in longer term T cell responses. Now, we report that cathelicidin drives severe EAE disease. It is released from neutrophils, microglia and endothelial cells throughout disease; its interaction with T cells potentiates Th17 differentiation in lymph nodes and Th17 to exTh17 plasticity and IFN-{gamma} production in the spinal cord. As a consequence, mice lacking cathelicidin are protected from severe EAE. In addition, we show that cathelicidin is produced by the same cell types in the active brain lesions in human MS disease. We propose that cathelicidin exposure results in highly activated, cytokine-producing T cells which drive autoimmunity; this is a mechanism through which neutrophils amplify inflammation in the central nervous system.

immunology↗

bioRxiv2021

Classical macrophage polarisation is limited by human β-defensin 3 via an autocrine IL-4 dependent process.

Human {beta}-defensin 3 (HBD3), is an anti-microbial host-defence peptide, that can rapidly enter macrophages to modulate TLR4 responses to lipopolysaccharide. However, the molecular mechanisms by which HBD3 exerts this anti-inflammatory influence remain unclear. Here, we show mice deleted for the orthologue of HBD3 have an increased acute lipopolysaccharide response in vivo. Furthermore, we found that HBD3 limited the response of macrophages to classical activation, and contemporaneously drove expression of IL-4. An increase in markers of alternative activation, and a change in metabolic flux was also observed. Consistent with these results, HBD3 enhanced the IL-4 mediated polarisation of naive macrophages. Finally, we demonstrate that the ability of HBD3 to limit macrophage classical activation requires IL-4R. These data reveal a previously unrecognised role for HBD3 in influencing the polarisation state of macrophages to enable a state conducive for repair and resolution. SYNOPSIS O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=131 SRC="FIGDIR/small/442606v2_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@f81c9aorg.highwire.dtl.DTLVardef@11dca23org.highwire.dtl.DTLVardef@c1e241org.highwire.dtl.DTLVardef@ed46ed_HPS_FORMAT_FIGEXP M_FIG C_FIG The anti-microbial host-defence peptide, Human {beta}-defensin 3 (HBD3), is shown here to modulate the inflammatory response to classical activation by promoting alternative activation through IL-4R, to enable a state conducive for repair and resolution. O_LIKnockout mice for the orthologous gene for HBD3, demonstrate increased acute lipopolysaccharide inflammatory response. C_LIO_LIHBD3 limited the classical activation of macrophages polarised with LPS/IFN{gamma} and drove expression of IL-4. Cells also displayed increase in alternative activation markers and promotion of oxidative phosphorylation. C_LIO_LIHBD3 enhanced the IL-4-mediated activation of naive macrophages. C_LIO_LIThe ability of HBD3 to limit macrophage classical activation and contemporaneously promote alternative activation required IL-4R. C_LI

immunology↗

bioRxiv2020

Ultra-pure isolation of low density neutrophils casts doubt on their exceptionality in health and disease

Low density neutrophils (LDNs) are described in a number of inflammatory conditions, cancers and infections and associated with immunopathology, and a mechanistic role in disease. The role of LDNs at homeostasis in healthy individuals has not been investigated. We have developed an isolation protocol that generates high purity LDNs from healthy donors. Healthy LDNs were identical to healthy NDNs, aside from reduced neutrophil extracellular trap formation. CD66b, CD16, CD15, CD10, CD54, CD62L, CXCR2, CD47 and CD11b were expressed at equivalent levels in LDNs and normal density neutrophils (NDNs) and underwent apoptosis and ROS production interchangeably. Healthy LDNs had no differential effect on CD4+ or CD8+ T cell proliferation or IFN{gamma} production compared with NDNs. LDNs were generated from healthy NDNs in vitro by activation with TNF, LPS or fMLF, suggesting a mechanism of LDN generation in disease however, we show neutrophilia in people with Cystic Fibrosis (CF) was not due to increased LDNs. LDNs are present in the neutrophil pool at homeostasis and have limited functional differences to NDNs. We conclude that increased LDN numbers in disease reflect the specific pathology or inflammatory environment and that neutrophil density alone is inadequate to classify discrete functional populations of neutrophils. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=115 SRC="FIGDIR/small/156588v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@1d10e01org.highwire.dtl.DTLVardef@1ee6bc3org.highwire.dtl.DTLVardef@1e5037dorg.highwire.dtl.DTLVardef@480797_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2020

The neutrophil antimicrobial peptide cathelicidin promotes Th17 differentiation

The host defence peptide cathelicidin (LL-37 in humans, mCRAMP in mice) is released from neutrophils by de-granulation, NETosis and necrotic cell death; it has potent antibacterial, antiviral and antifungal activity as well as being a powerful immunomodulator. It is released in proximity to CD4+ T cells during inflammatory and infectious disease but its impact on T cell phenotype is scarcely understood. Here we demonstrate that cathelicidin is a powerful Th17 potentiating factor which increases expression of the aryl hydrocarbon receptor (AHR) and the ROR{gamma}t transcription factor, in a TGF-{beta}1-dependent manner. We show that cathelicidin induces IL-17F production in particular, and that its induction of IL-17A+F+ double producing cells is dependent on AHR while its induction of IL-17F single producing cells is not. In the presence of TGF-{beta}1, cathelicidin profoundly suppressed IL-2 and down-regulated T-bet, specifically directing T cells away from Th1 and into a Th17 phenotype. Strikingly, Th17, but not Th1 cells were protected from apoptotic death by cathelicidin, in the first example of a neutrophil-released mediator inducing survival of a T cell subset. Finally, we show that cathelicidin is released by neutrophils in mouse lymph nodes following inoculation of heat-killed Salmonella typhimurium and that cathelicidin-deficient mice have suppressed Th17 responses during inflammation, but not at steady state. We propose that the release of cathelicidin by neutrophils is required for maximal Th17 differentiation and IL-17 production by CD4+ T cells, and that this is one method by which early neutrophilia directs subsequent adaptive immune responses with some sophistication.

immunology↗

bioRxiv2017

Evaluating the Role of Cell-free Fetal DNA in Inflammation and Spontaneous Preterm Birth.

Preterm birth is the leading cause of neonatal mortality. While spontaneous preterm birth (sPTB) is the cause of over 70% of PTB, the pathogenesis behind sPTB remains unclear. Cell-free fetal DNA (cff-DNA) originates from the placenta and is increased in women who develop PTB. It has been demonstrated that fetal DNA is hypomethylated and is pro-inflammatory. The pro-inflammatory properties of placental-derived DNA, the effects of placental inflammation on the production of cff-DNA, and its significance in the pathogenesis of PTB are unknown.\n\nUsing a human placental explant model, we analysed the effect of lipopolysaccharide (LPS) stimulation on cff-DNA production, and used the cff-DNA generated by these explants to examine the methylation profile and in-vitro pro-inflammatory properties of cff-DNA. LPS caused significant production of TNF- from placental explants, but did not significantly increase the cff-DNA production. Placental-derived cff-DNA, was found to have a small proportion of unmethylated CpG motifs, but was more similar to adult DNA than to more highly unmethylated E-coli DNA. However, cff-DNA did not elicit production of inflammatory cytokines (IL-6, IL-8, TNF- and CXCL10) by peripheral blood mononuclear cells from pregnant women. Furthermore, in contrast to LPS, intra-uterine injections of mouse placental DNA did not decrease time to delivery in an in-vivo mouse PTB model compared to control animals.\n\nThis study demonstrates that placental inflammation does not increase the production of cff-DNA in placental explants, and cff-DNA alone is not sufficient to elicit an inflammatory response in human PBMC cultures ex-vivo. It also shows that mouse placental DNA does not cause PTB in-vivo. This suggests that cff-DNA might be predominantly an effect of parturition and not a principal causative agent.

immunology↗