Single-cell RNA sequencing analysis of vestibular schwannoma reveals functionally distinct macrophage subsets.

BACKGROUND: Vestibular schwannomas (VSs) remain a challenge due to their anatomical location and propensity to growth. Macrophages are present in VS but their roles in VS pathogenesis remains unknown. OBJECTIVES: The objective was to assess phenotypic and functional profile of macrophages in VS with single-cell RNA sequencing (scRNAseq). METHODS: scRNAseq was carried out in three VS samples to examine characteristics of macrophages in the tumour. RT-qPCR was carried out on 10 VS samples for CD14, CD68 and CD163 and a panel of macrophage-associated molecules. RESULTS: scRNAseq revealed macrophages to be a major constituent of VS microenvironment with three distinct subclusters based on gene expression. The subclusters were also defined by expression of CD163, CD68 and IL-1ß. AREG and PLAUR were expressed in the CD68+CD163+IL-1ß+ subcluster, PLCG2 and NCKAP5 were expressed in CD68+CD163+IL-1ß- subcluster and AUTS2 and SPP1 were expressed in the CD68+CD163-IL-1ß+ subcluster. RT-qPCR showed expression of several macrophage markers in VS of which CD14, ALOX15, Interleukin-1ß, INHBA and Colony Stimulating Factor-1R were found to have a high correlation with tumour volume. CONCLUSIONS: Macrophages form an important component of VS stroma. scRNAseq reveals three distinct subsets of macrophages in the VS tissue which may have differing roles in the pathogenesis of VS.

Complications of acute mastoiditis in a paediatric population at a UK Tertiary Centre: A retrospective review.

OBJECTIVES: Acute mastoiditis (AM) and its associated intra and extracranial complications are rare complications of acute otitis media. However, they are associated with a high morbidity. The management of AM with complications carries significant variations in approach. We aimed to evaluate the presentation of children with AM with complications to a tertiary referral centre in the United Kingdom and describe evolution of the treatment approaches. METHODS: We undertook a retrospective chart review of all children admitted with AM to the University Hospitals of Leicester between 2013 and 2022. RESULTS: Twenty-seven children were included in this study: 7 patients had sigmoid sinus thrombosis (SST), 4 had an intracranial collection, 3 had cranial nerve palsy and 16 had a subperiosteal abscess (SPA); some patients had more than 1 complication. In this study, treatment of SPA with incision and drainage (I&D) and grommet insertion was effective, as all patients treated with grommet insertion and I&D recovered well and did not require a subsequent cortical mastoidectomy. All patients with SST received anticoagulation and intravenous (IV) antibiotics; surgical input consisted of grommet insertion alone and cortical mastoidectomy was not routinely performed in these patients. CONCLUSION: In our series, management of SPA with grommet insertion and drainage had good outcomes. SST management mainly consisted of IV antibiotics, anticoagulation and grommet insertion with good recovery. The evidence to guide the management of complications of mastoiditis is of poor quality and further research is needed to clarify the optimal management of these complications.

Fibroblasts Derived From Vestibular Schwannoma Express Protumorogenic Markers.

BACKGROUND AND AIM: Vestibular schwannomas (VSs), despite being histologically benign, cause significant morbidity because of their challenging intracranial location and the propensity for growth. The role of the stroma and particularly fibroblasts, in the progression of VS, is not completely understood. This study examines the profile of fibroblasts in VS. METHODS: Seventeen patients undergoing surgical excision of VS were recruited into the study. Reverse transcription with quantitative polymerase chain reaction (RT-qPCR) was performed on VS tissue samples and fibroblast-associated molecules examined. Immunofluorescence and immunohistochemistry in VS tissue were used to study the expression of fibroblast markers CD90 and podoplanin in situ. Fibroblast cultures were established from VS, and RT-qPCR analysis was performed on a panel of fibroblast markers on VS and control tissue fibroblasts. RESULTS: Several fibroblast-associated molecules including members of galectin family and matrix metalloproteinases were found to be expressed in VS tissue on RT-qPCR analysis. In situ, expression of CD90 and podoplanin was observed in VS tissue both on immunohistochemistry and immunofluorescence. RT-qPCR analysis of fibroblasts from VS and control vestibular neuroepithelium (NE) showed a higher expression of several molecules of the galectin and matrix metalloproteinases family on VS fibroblasts compared with NE fibroblasts. CONCLUSION: This work examines fibroblasts from VS and shows qualitative differences from NE fibroblasts on RT-qPCR. Further understanding of the fibroblast function in the progression of VS will potentially unveil new targets to manage VS growth.

TLR9 Mediated Tumor-Stroma Interactions in Human Papilloma Virus (HPV)-Positive Head and Neck Squamous Cell Carcinoma Up-Regulate PD-L1 and PD-L2.

Background: The co-inhibitory receptor PD-1 is expressed in many tumors including head and neck squamous cell carcinoma (HNSCC) and is an important immunotherapy target. However, the role of PD-1 ligands, PD-L1, and particularly PD-L2, in the tumor-stromal cell interactions that cause a tumor-permissive environment in HNSCC is not completely understood and is the focus of our study. Methods: Expression of PD-L1 and PD-L2 was analyzed by immunohistochemistry in situ in HNSCC tumor tissue. Co-cultures were established between stromal cells (fibroblasts and macrophages) and human papilloma virus (HPV)-positive and HPV-negative HNSCC cell lines (HNSCCs) and PD-1 ligands expression was analyzed using flow cytometry. Results: PD-L1 and PD-L2 were expressed both in tumor cells and stroma in HNSCC tissue in situ. In vitro, basal expression of PD-L1 and PD-L2 was low in HNSCCs and high on fibroblasts and macrophages. Interestingly, HPV-positive but not HPV-negative HNSCCs increased the expression of both PD-1 ligands on fibroblasts upon co-culture. This effect was not observed with macrophages. Conversely, both fibroblasts and macrophages increased PD-1 ligands on HPV-positive HNSCCs, whilst this was not observed in HPV-negative HNSCCs. Crucially, we demonstrate that up-regulation of PD-L1 and PD-L2 on fibroblasts by HPV-positive HNSCCs is mediated via TLR9. Conclusions: This work demonstrates in an in vitro model that HPV-positive HNSCCs regulate PD-L1/2 expression on fibroblasts via TLR9. This may open novel avenues to modulate immune checkpoint regulator PD-1 and its ligands by targeting TLR9.

Principles of ear nose and throat surgery for pregnant women.

Management of the pregnant surgical patient is challenging. The surgical procedure is usually postponed until the postpartum period, although this may not be possible in emergency situations. This article highlights the optimal management of the pregnant woman requiring ear nose and throat surgery.

Impact of Chronic Suppurative Otitis Media in Pediatric Cochlear Implant Recipients-Insight into the Challenges from a Tertiary Referral Center in UK.

OBJECTIVE: Analyze the presentation and evolution of chronic suppurative otitis media (CSOM) in children with cochlear implants (CI) and explore the merit of early intervention. STUDY DESIGN: Retrospective patient review. SETTING: Tertiary referral hospital and cochlear implant programme. PATIENTS: Children with a CI who developed CSOM. INTERVENTION: Tympanoplasty. MAIN OUTCOME MEASURES: Disease control, recurrence of cholesteatoma, cochlear implant preservation. RESULTS: Eight children fit our inclusion criteria with a mean follow up of 8 years. Onset of CSOM symptoms was observed on an average of 5 years after implantation (range, 2-13 yr) and led to surgical intervention in an average of 15.6 months following symptom onset. Cholesteatoma was found in four of the eight patients. Of these, one patient underwent a subtotal petrosectomy and explantation with reimplantation at the same stage but the reimplant failed to function and was explanted subsequently. One patient was initially managed by a canal wall up mastoidectomy and explantation but went on to require subtotal petrosectomy and labyrinthectomy for recurrent disease. One patient underwent a subtotal petrosectomy with explantation and is awaiting a reimplantation. The fourth patient had limited disease around the electrodes that was excised without compromising the implant. In the group of patients with CSOM without cholesteatoma, one underwent an explantation due to recurrent ear infections and a subsequent cartilage tympanoplasty for a retracted eardrum. The remaining three patients underwent successful excision of retraction pockets and repair of eardrums using cartilage with the implant in situ. A mean follow up of 2 years after the implant preservation surgeries shows good functioning of the CI. CONCLUSION: Early recognition of CSOM is paramount in patients with CI as delay in treatment can result in the infection spreading via the cochleostomy resulting in loss of the cochlea. Recurrent ear infections in an implanted ear should prompt early examination to exclude the presence of middle ear disease, which may require anesthesia in a young child.

Proteasome-mediated reduction in proapoptotic molecule Bim renders CD4⁺CD28null T cells resistant to apoptosis in acute coronary syndrome.

BACKGROUND: The number of CD4(+)CD28(null) (CD28(null)) T cells, a unique subset of T lymphocytes with proinflammatory and cell-lytic phenotype, increases markedly in patients with acute coronary syndrome (ACS). ACS patients harboring high numbers of CD28(null) T cells have increased risk of recurrent severe acute coronary events and unfavorable prognosis. The mechanisms that govern the increase in CD28(null) T cells in ACS remain elusive. We investigated whether apoptosis pathways regulating T-cell homeostasis are perturbed in CD28(null) T cells in ACS. METHODS AND RESULTS: We found that CD28(null) T cells in ACS were resistant to apoptosis induction via Fas-ligation or ceramide. This was attributable to a dramatic reduction in proapoptotic molecules Bim, Bax, and Fas in CD28(null) T cells, whereas antiapoptotic molecules Bcl-2 and Bcl-xL were similar in CD28(null) and CD28(+) T cells. We also show that Bim is phosphorylated in CD28(null) T cells and degraded by the proteasome. Moreover, we demonstrate for the first time that proteasomal inhibition restores the apoptosis sensitivity of CD28(null) T cells in ACS. CONCLUSIONS: We show that CD28(null) T cells in ACS harbor marked defects in molecules that regulate T-cell apoptosis, which tips the balance in favor of antiapoptotic signals and endows these cells with resistance to apoptosis. We demonstrate that the inhibition of proteasomal activity allows CD28(null) T cells to regain sensitivity to apoptosis. A better understanding of the molecular switches that control the apoptosis sensitivity of CD28(null) T cells may reveal novel strategies for targeted elimination of these T cells in ACS patients.

Cochlin in autoimmune inner ear disease: is the search for an inner ear autoantigen over?

DEFINITION: Autoimmune inner ear disease (AIED) is characterised by a rapidly progressive, often fluctuating, bilateral sensorineural hearing loss over a period of weeks to months. It is an uncommon disease accounting for less than 1% of all cases of hearing impairment or dizziness. The diagnosis is often missed and this impacts on the prognosis as the condition responds well to steroids and immunosuppressants if recognised early. LACUNA IN KNOWLEDGE: No useful specific test for autoimmunity affecting the inner ear exists. OBJECTIVE OF STUDY: To gather evidence regarding cochlin in AIED. METHODOLOGY: Systematic review of human studies and animal experimental studies on inner ear antigens was undertaken. SEARCH STRATEGY: We searched MEDLINE (1965-2012), and Pubmed for relevant studies. A combination of key words for inner ear, autoimmunity (autoimmune, immune mediated) and cochlin were used. RESULTS: A number of antigens have been implicated in autoimmune inner ear disease. Cochlin is a major component of the extracellular matrix in the inner ear and a promising candidate. We present evidence in literature on the role of this protein in the pathogenesis of autoimmune inner ear disease.

Tuberculous retropharyngeal abscess revisited.

Retropharyngeal tubercular abscess is an uncommon cause of neck pain and dysphagia in the developed world. In this report, we describe an insidiously presenting retropharyngeal abscess treated successfully with intraoral aspiration and antitubercular chemotherapy. A 33-year-old female patient presented with neck pain and dysphagia. MRI revealed a large retropharyngeal abscess that was aspirated intraorally under local anaesthetic. Diagnosis of tuberculosis (TB) was confirmed by positive culture. The patient improved significantly following the initiation of antitubercular therapy. Retropharyngeal abscess is a recognised presentation of TB. The treatment is mainly medical with combination of specific antitubercular antibiotics, and aspiration may be sufficient for abscess drainage.

High levels of costimulatory receptors OX40 and 4-1BB characterize CD4+CD28null T cells in patients with acute coronary syndrome.

RATIONALE: Patients with acute coronary syndrome (ACS) predisposed to recurrent coronary events have an expansion of a distinctive T-cell subset, the CD4(+)CD28(null) T cells. These cells are highly inflammatory and cytotoxic in spite of lacking the costimulatory receptor CD28, which is crucial for optimal T cell function. The mechanisms that govern CD4(+)CD28(null) T cell function are unknown. OBJECTIVE: Our aim was to investigate the expression and role of alternative costimulatory receptors in CD4(+)CD28(null) T cells in ACS. METHODS AND RESULTS: Expression of alternative costimulatory receptors (inducible costimulator, OX40, 4-1BB, cytotoxic T lymphocyte associated antigen-4, programmed death-1) was quantified in CD4(+)CD28(null) T cells from circulation of ACS and stable angina patients. Strikingly, in ACS, levels of OX40 and 4-1BB were significantly higher in circulating CD4(+)CD28(null) T cells compared to classical CD4(+)CD28(+) T lymphocytes. This was not observed in stable angina patients. Furthermore, CD4(+)CD28(null) T cells constituted an important proportion of CD4(+) T lymphocytes in human atherosclerotic plaques and exhibited high levels of OX40 and 4-1BB. In addition, the ligands for OX40 and 4-1BB were present in plaques and also expressed on monocytes in circulation. Importantly, blockade of OX40 and 4-1BB reduced the ability of CD4(+)CD28(null) T cells to produce interferon-γ and tumor necrosis factor-α and release perforin. CONCLUSIONS: Costimulatory pathways are altered in CD4(+)CD28(null) T cells in ACS. We show that the inflammatory and cytotoxic function of CD4(+)CD28(null) T cells can be inhibited by blocking OX40 and 4-1BB costimulatory receptors. Modulation of costimulatory receptors may allow specific targeting of this cell subset and may improve the survival of ACS patients.

Decreased levels of alternative co-stimulatory receptors OX40 and 4-1BB characterise T cells from head and neck cancer patients.

BACKGROUND AND AIM: Head and neck cancers (HNC) are aggressive tumours. Tumour-specific T cells are frequently identified in patients with cancer, although they fail to control tumour progression. A family of proteins called co-stimulatory receptors regulate the function of T cells and may account for T cell dysfunction in cancer. Our aim was to characterise co-stimulatory receptors on T cells in HNC patients to identify novel targets for immunotherapy. METHODS: Peripheral blood mononuclear cells were isolated from HNC patients and healthy controls and the expression of co-stimulatory (OX40, 4-1BB, ICOS) and co-inhibitory (CTLA-4, PD1) receptors was analysed on CD4(+) and CD8(+) T cells using flow cytometry. RESULTS: We found that the levels of co-stimulatory receptors OX40 and 4-1BB were significantly lower on CD4(+) T cells from HNC patients. This was more pronounced in locally advanced tumours (T3/T4) compared to early carcinomas (T1/T2). PD-1 levels were higher on CD8(+) T cells in HNC patients compared to controls. Human papilloma virus (HPV)-specific CD8(+) T cells appeared to be more affected than Influenza-specific T cells. CONCLUSIONS: Our results indicate that expression of co-stimulatory receptors on T cells from HNC patients is imbalanced with a preponderance of inhibitory signals, and reduction of stimulatory signals, especially in advanced disease. Restoring this balance could improve T cell therapy outcomes in HNC.

Diagnostic accuracy of white cell count and C-reactive protein for assessing the severity of paediatric appendicitis.

OBJECTIVES: Simple investigations like white cell count (WCC) and C-reactive protein (CRP) may help to improve the accuracy of diagnosis in paediatric appendicitis. We evaluated the diagnostic accuracy of WCC and CRP for the severity of acute appendicitis in children. DESIGN: Cross-sectional study. SETTING: This study was conducted on all children who underwent open appendectomy from January 2007 to December 2008 at a District General Hospital. Data regarding demographics, WCC, CRP, histology and postoperative complications were analysed. PARTICIPANTS: All children who underwent open appendectomy during the study period. MAIN OUTCOME MEASURES: Diagnostic accuracy of WCC and CRP for simple acute appendicitis and a perforated appendix. RESULTS: Out of 204 patients, 112 (54.9%) were girls. At surgery, appendix was grossly inflamed in 175 of which 32 had perforation. Histology revealed simple acute appendicitis in 135 (66.2%) and gangrenous appendicitis in 32 (15.7%). The rest were normal. The duration of symptoms, temperature, length of stay, WCC and CRP were significantly worse in the perforated group (P value <0.05). Postoperative complications included wound infection (n = 18), pelvic collection (n = 5) and intestinal obstruction (n = 6); and were more common among patients with a perforated appendix (P value <0.05). WCC had a higher diagnostic accuracy and higher sensitivity than CRP in diagnosing simple acute appendicitis. The combined sensitivity of WCC and CRP increased to 95% and 100% for the diagnosis of simple acute appendicitis and a perforated appendix, respectively. CONCLUSION: Accuracy of WCC is higher than CRP for diagnosing simple acute appendicitis. The combined sensitivity of WCC and CRP increases for simple acute appendicitis as well as a perforated appendix.

Identification and characterization of a lupus suppressor 129 locus on chromosome 3.

The 129-derived Sle16 is a susceptibility locus for systemic autoimmunity when present on the C57BL/6 (B6) background. Genetic analysis of a (129xB6)F2 cross identified a region from the B6 chromosome 3 (Sle18) with positive linkage to antinuclear Abs. In this study, we have generated a B6 congenic strain harboring the 129 allele of Sle18 and intercrossed this line with the lupus-prone B6.129-Sle16 strain. The presence of the 129-Sle18 allele in the B6.129-Sle16Sle18 double congenic mice suppressed the development of Sle16-mediated autoantibody production and ameliorated the renal pathology. The 129-Sle18 locus rectified the B cell abnormalities detected in the B6.129-Sle16 mice, such as the reduction in the percentage of marginal zone B and B1a cells and the increased number of germinal centers. The B6.129-Sle16Sle18 spleens still displayed an increased percentage of activated T and B cells. However, in the B6.129-Sle16Sle18 strain the percentage of naive T cells was equivalent to that in B6.129-Sle18 and B6 mice and these cells showed a reduced proliferative response to anti-CD3 stimulation compared with B6.129-Sle16 T cells. There was a significant increase in the percentage of CD4(+)FoxP3(+)regulatory T cells in all congenic strains. These cells had normal regulatory function when tested in vitro. Thus, 129-Sle18 represents a novel, non-MHC lupus-suppressor locus probably operating as a functional modifier of B cells that, in combination with other factors, leads to lupus resistance. Further characterization of this locus will help to uncover the immune mechanism(s) conferring protection against lupus.

Mice lacking C1q or C3 show accelerated rejection of minor H disparate skin grafts and resistance to induction of tolerance.

Complement activation is known to have deleterious effects on organ transplantation. On the other hand, the complement system is also known to have an important role in regulating immune responses. The balance between these two opposing effects is critical in the context of transplantation. Here, we report that female mice deficient in C1q (C1qa(-/-)) or C3 (C3(-/-)) reject male syngeneic grafts (HY incompatible) at an accelerated rate compared with WT mice. Intranasal HY peptide administration, which induces tolerance to syngeneic male grafts in WT mice, fails to induce tolerance in C1qa(-/-) or C3(-/-) mice. The rejection of the male grafts correlated with the presence of HY D(b)Uty-specific CD8(+) T cells. Consistent with this, peptide-treated C1qa(-/-) and C3(-/-) female mice rejecting male grafts exhibited more antigen-specific CD8(+)IFN-gamma(+) and CD8(+)IL-10(+) cells compared with WT females. This suggests that accumulation of IFN-gamma- and IL-10-producing T cells may play a key role in mediating the ongoing inflammatory process and graft rejection. Interestingly, within the tolerized male skin grafts of peptide-treated WT mice, IFN-gamma, C1q and C3 mRNA levels were higher compared to control female grafts. These results suggest that C1q and C3 facilitate the induction of intranasal tolerance.

C1q enhances IFN-gamma production by antigen-specific T cells via the CD40 costimulatory pathway on dendritic cells.

Dendritic cells (DCs) are known to produce C1q, the initiator of the classical complement pathway. We demonstrate that murine DCs deficient in C1q (C1qa(-/-)) are poorer than wild-type (WT) DCs at eliciting the proliferation and Th1 differentiation of antigen-specific T cells. These defects result from decreased production of IL-12p70 by C1qa(-/-) DCs and impaired expression of costimulatory molecules CD80 and CD86 in response to CD40 ligation. The defective production of IL-12p70 and the reduced expression of CD80 and CD86 by C1qa(-/-) DCs were specifically mediated via CD40 ligation, as normal levels of IL-12p70 and CD80/86 were observed after ligation of Toll-like receptors (TLRs) on C1qa(-/-) DCs. CD40 ligation on C1qa(-/-) DCs, but not TLR ligation, results in decreased phosphorylation of p38 and ERK1/2 kinases. A strong colocalization of CD40 and C1q was observed by confocal microscopy upon CD40 ligation (but not TLR ligation) on DCs. Furthermore, human DCs from 2 C1q-deficient patients were found to have impaired IL-12p70 production in response to CD40L stimulation. Our novel data suggest that C1q augments the production of IL-12p70 by mouse and human DCs after CD40 triggering and plays important roles in sustaining the maturation of DCs and guiding the activation of T cells.

Innate responses to Aspergillus: role of C1q and pentraxin 3 in nasal polyposis.

BACKGROUND: Pentraxin 3 (PTX3) and complement component C1q are humoral factors of innate immunity, produced at sites of inflammation, and are essential in immune defense against several microbes such as Aspergillus, which is commonly implicated in nasal polyposis. METHODS: PTX3 and C1q were measured in nasal polyp tissue, normal nasal mucosa, and serum of patients and healthy subjects. Immunohistochemistry for the two proteins was done on normal nasal mucosa and nasal polyps. In addition, PTX3 and C1q production from mononuclear cells from patients and healthy subjects was assessed. RESULTS: Normal nasal mucosa was found to have 100-fold higher levels of PTX3 compared with serum. No measurable local increase of PTX3 was observed in polyps compared with normal mucosa. Immunohistochemistry revealed PTX3 expression in the lining of blood vessels both within normal mucosa and nasal polyps. PTX3 also was present in mononuclear cells infiltrating nasal polyps. C1q levels were higher in polyps than in normal nasal mucosa. CONCLUSION: High levels of PTX3 are present in normal nasal mucosa, suggesting a role in the maintenance of tissue homeostasis. Elevated C1q levels in nasal polyps might be indicative of an ongoing inflammatory response in the nasal mucosa in these patients.

The tissue pentraxin PTX3 limits C1q-mediated complement activation and phagocytosis of apoptotic cells by dendritic cells.

Pentraxins (PTX) and complement belong to the humoral arm of the innate immune system and have essential functions in immune defense to microbes and in scavenging cellular debris. The prototypic long PTX, PTX3, and the first component of the classical complement pathway, C1q, are innate opsonins involved in the disposal of dying cells by phagocytes. Whether the interaction between various innate opsonins impacts on their function is not fully understood. We show here that characterized Toll-like receptor (TLR) ligands elicit the production of C1q and PTX3 by immature dendritic cells (DC). Moreover, these molecules bind to dying cells with similar kinetics, although they recognize different domains on the cell membranes. PTX3 binds in the fluid phase to C1q, decreasing C1q deposition and subsequent complement activation on apoptotic cells. C1q increases the phagocytosis of apoptotic cells by DC and the release of interleukin-12 in the presence of TLR4 ligands and apoptotic cells; PTX3 inhibits both events. Moreover, PTX3 inhibited the cross-presentation of the MELAN-A/melanoma antigen-reactive T cell 1 (MART-1) tumor antigen expressed by dying cells, even in the presence of C1q. These results suggest that interaction of C1q and PTX3 influences the clearance of apoptotic cells by DC. The coordinated induction by primary, proinflammatory signals of C1q and PTX3 and their reciprocal regulation during inflammation influences the clearance of apoptotic cells by antigen-presenting cells and possibly plays a role in immune homeostasis.

The pattern recognition receptor PTX3 is recruited at the synapse between dying and dendritic cells, and edits the cross-presentation of self, viral, and tumor antigens.

Pentraxins are soluble pattern recognition receptors with a dual role: protection against extracellular microbes and autoimmunity. The mechanisms by which they accomplish these tasks are not yet fully understood. Here we show that the prototypic long pentraxin PTX3 is specifically recruited at both sides of the phagocytic synapse between dendritic cells (DCs) and dying cells and remains stably bound to the apoptotic membranes (estimated half-time > 36 hours). Apoptotic cells per se influence the production of PTX3 by maturing DCs. When both microbial stimuli and dying cells are present, PTX3 behaves as a flexible adaptor of DC function, regulating the maturation program and the secretion of soluble factors. Moreover a key event associated with autoimmunity (ie, the cross-presentation of epitopes expressed by apoptotic cells to T cells) abates in the presence of PTX3, as evaluated using self, viral, and tumor-associated model antigens (vinculin, NS3, and MelanA/MART1). In contrast, PTX3 did not influence the presentation of exogenous soluble antigens, an event required for immunity against extracellular pathogens. These data suggest that PTX3 acts as a third-party agent between microbial stimuli and dying cells, contributing to limit tissue damage under inflammatory conditions and the activation of autoreactive T cells.

Release of high mobility group box 1 by dendritic cells controls T cell activation via the receptor for advanced glycation end products.

High mobility group box 1 (HMGB1) is an abundant and conserved nuclear protein that is released by necrotic cells and acts in the extracellular environment as a primary proinflammatory signal. In this study we show that human dendritic cells, which are specialized in Ag presentation to T cells, actively release their own HMGB1 into the extracellular milieu upon activation. This secreted HMGB1 is necessary for the up-regulation of CD80, CD83, and CD86 surface markers of human dendritic cells and for IL-12 production. The HMGB1 secreted by dendritic cells is also required for the clonal expansion, survival, and functional polarization of naive T cells. Using neutralizing Abs and receptor for advanced glycation end product-deficient (RAGE(-/-)) cells, we demonstrate that RAGE is required for the effect of HMGB1 on dendritic cells. HMGB1/RAGE interaction results in downstream activation of MAPKs and NF-kappaB. The use of an ancient signal of necrosis, HMGB1, by dendritic cells to sustain their own maturation and for activation of T lymphocytes represents a profitable evolutionary mechanism.