Blockade of the Phagocytic Receptor MerTK on Tumor-Associated Macrophages Enhances P2X7R-Dependent STING Activation by Tumor-Derived cGAMP.

Clearance of apoptotic cells by macrophages prevents excessive inflammation and supports immune tolerance. Here, we examined the effect of blocking apoptotic cell clearance on anti-tumor immune response. We generated an antibody that selectively inhibited efferocytosis by phagocytic receptor MerTK. Blockade of MerTK resulted in accumulation of apoptotic cells within tumors and triggered a type I interferon response. Treatment of tumor-bearing mice with anti-MerTK antibody stimulated T cell activation and synergized with anti-PD-1 or anti-PD-L1 therapy. The anti-tumor effect induced by anti-MerTK treatment was lost in Stinggt/gt mice, but not in Cgas-/- mice. Abolishing cGAMP production in Cgas-/- tumor cells, depletion of extracellular ATP, or inactivation of the ATP-gated P2X7R channel also compromised the effects of MerTK blockade. Mechanistically, extracellular ATP acted via P2X7R to enhance the transport of extracellular cGAMP into macrophages and subsequent STING activation. Thus, MerTK blockade increases tumor immunogenicity and potentiates anti-tumor immunity, which has implications for cancer immunotherapy.

The Role of Noncoding RNA Antisense Transcript of the B-Cell Translocation Gene 3 Regulation of BTG3 in Pancreatic Ductal Adenocarcinoma Tumor Progression.

Background: Antisense transcript of the B-cell translocation gene 3 (ASBEL) is a highly conserved antisense non-coding RNA (ncRNA) and participates in a variety of biological processes. However, the ASBEL expression status in pancreatic ductal adenocarcinoma (PDAC) and its correlation with BTG3 expression and tumor cell progression were not completely clear. Objective: We conducted cell experiments and animal experiments to confirm that ASBEL plays a crucial role in the tumorigenesis of PDAC by targeting BTG3. Methods: ASBEL regulation in PDAC tumorigenesis was evaluated using Western blotting, quantitative polymerase chain reaction, Cell Counting Kit-8 assay, flow cytometry, and cell transfection. We also evaluated the expression of ASBEL and BTG3 in tumor tissues and cells using Western blotting and quantitative real-time polymerase chain reaction. Finally, we explored the role of ASBEL in tumor development by silencing or overexpressing ASBEL gene in AsPC-1 or CFPAC-1 cells, respectively, and evaluated the antitumor activity in vivo using an ASBEL antagonist. Results: Our study revealed the expression of ASBEL in all pancreatic cell lines. The expression level of ASBEL in tumor tissues was found to be higher than that of paracarcinomatous tissues. ASBEL suppresses expression of BTG3, enhances proliferation and suppresses apoptosis, and promotes migration and invasion in pancreatic cancer cell. Antagonist regulates the expression of ASBEL in AsPC-1, and suppresses tumor growth in xenograft mouse model. Conclusions: Our results indicate that ASBEL may play a tumor-promoting factor in PDAC by targeting BTG3 and could be as an important biomarker for PDAC treatment. (Curr Ther Res Clin Exp. 2023; 84:XXX-XXX).

PEGylation of anti-MerTK Antibody Modulates Ocular Biodistribution.

Here, we explore whether PEGylation of antibodies can modulate their biodistribution to the eye, an organ once thought to be immune privileged but has recently been shown to be accessible to IV-administered large molecules, such as antibodies. We chose to PEGylate an anti-MerTK antibody, a target with known potential for ocular toxicity, to minimize biodistribution to retinal pigment epithelial cells (RPEs) in the eye by increasing the hydrodynamic volume of the antibody. We used site-specific conjugation to an engineered cysteine on anti-MerTK antibody to chemically attach 40-kDa branched or linear PEG polymers. Despite reduced binding to MerTK on cells, site-specifically PEGylated anti-MerTK retained similar potency in inhibiting MerTK-mediated macrophage efferocytosis of apoptotic cells. Importantly, we found that PEGylation of anti-MerTK significantly reduced MerTK receptor occupancy in RPE cells in both naïve mice and MC-38 tumor-bearing mice, with the branched PEG exhibiting a greater effect than linear PEG. Furthermore, similar to unconjugated anti-MerTK, PEGylated anti-MerTK antibody triggered type I IFN response and exhibited antitumor effect in syngeneic mouse tumor studies. Our results demonstrate the potential of PEGylation to control ocular biodistribution of antibodies.

Cytopathological characteristics of angioimmunoblastic T-cell lymphoma diagnosed by fine needle aspiration.

OBJECTIVE: To analyse the cytopathological features of fine needle aspiration (FNA) in angioimmunoblastic T-cell lymphoma (AITL) diagnostics. METHODS: Fine needle aspiration lymph node biopsy samples from 12 patients with AITL were collected at a single centre between January 2014 and December 2020. The clinical, cytological and histopathological characteristics were retrospectively analysed. RESULTS: Three male and six female patients with AITL who had a median onset age of 65 years (range 51-74 years) and a mean follow-up period of 29 months (range 12-47 months) were included. The FNA cytological and morphological analysis of the reactive lymph node background revealed diffusely distributed non-homogeneous mixed lymphocytes, including mature small lymphocytes, medium-sized lymphoid cells, immune cells, and plasma cells; some mixed eosinophils, macrophages, and an occasional mixture of visible and medium-sized lymphocytes and epithelioid cells were observed. Mitotically active lymphocytes and sporadic pigmented bodies were observed occasionally. An abnormal proliferation of follicular dendritic cells observed under the microscope is important for AITL diagnosis, and these cells are often distributed in a scattered pattern of small clusters with many nuclear morphologies. Branched capillaries are another important diagnostic clue. Two patients with AITL who achieved clinical remission after treatment experienced recurrence and were diagnosed using FNA and cell block immunohistochemistry. CONCLUSIONS: Fine needle aspiration provides clues for the diagnosis of AITL in special clinical situations, and cell block immunohistochemistry is worthy of further exploration.

Cutting edge: inhaled antigen upregulates retinaldehyde dehydrogenase in lung CD103+ but not plasmacytoid dendritic cells to induce Foxp3 de novo in CD4+ T cells and promote airway tolerance.

Dendritic cell (DC)-T cell interactions that underlie inducible/adaptive regulatory T cell generation and airway tolerance are not well understood. In this study, we show that mice lacking CD11c(hi) lung DCs, but containing plasmacytoid DCs (pDCs), fail tolerization with inhaled Ag and cannot support Foxp3 induction in vivo in naive CD4(+) T cells. CD103(+) DCs from tolerized mice efficiently induced Foxp3 in cocultured naive CD4(+) T cells but pDCs and lung macrophages failed to do so. CD103(+) DCs, but not pDCs or lung macrophages, upregulated the expression of retinaldehyde dehydrogenase 2 (aldh1a2), which is key for the production of retinoic acid, a cofactor for TGF-ß for Foxp3 induction. Batf3(-/-) mice, selectively lacking CD103(+) DCs, failed tolerization by inhaled Ag. Collectively, our data show that pulmonary tolerance is dependent on CD103(+) DCs, correlating with their ability to upregulate aldh1a2, which can promote Foxp3 expression in T cells.

TNF-alpha from inflammatory dendritic cells (DCs) regulates lung IL-17A/IL-5 levels and neutrophilia versus eosinophilia during persistent fungal infection.

Aspergillus fumigatus is commonly associated with allergic bronchopulmonary aspergillosis in patients with severe asthma in which chronic airway neutrophilia predicts a poor outcome. We were able to recapitulate fungus-induced neutrophilic airway inflammation in a mouse model in our efforts to understand the underlying mechanisms. However, neutrophilia occurred in a mouse strain-selective fashion, providing us with an opportunity to perform a comparative study to elucidate the mechanisms involved. Here we show that TNF-α, largely produced by Ly6c(+)CD11b(+) dendritic cells (DCs), plays a central role in promoting IL-17A from CD4(+) T cells and collaborating with it to induce airway neutrophilia. Compared with C57BL/6 mice, BALB/c mice displayed significantly more TNF-α-producing DCs and macrophages in the lung. Lung TNF-α levels were drastically reduced in CD11c-DTR BALB/c mice depleted of CD11c+ cells, and TNF-α-producing Ly6c(+)CD11b(+) cells were abolished in Dectin-1(-/-) and MyD88(-/-) BALB/c mice. TNF-α deficiency itself blunted accumulation of inflammatory Ly6c(+)CD11b(+) DCs. Also, lack of TNF-α decreased IL-17A but promoted IL-5 levels, switching inflammation from a neutrophil to eosinophil bias resembling that in C57BL/6 mice. The TNF-α(low) DCs in C57BL/6 mice contained more NF-κB p50 homodimers, which are strong repressors of TNF-α transcription. Functionally, collaboration between TNF-α and IL-17A triggered significantly higher levels of the neutrophil chemoattractants keratinocyte cytokine and macrophage inflammatory protein 2 in BALB/c mice. Our study identifies TNF-α as a molecular switch that orchestrates a sequence of events in DCs and CD4 T cells that promote neutrophilic airway inflammation.

Diagnostic Significance of Ultrasound-Guided Fine-Needle Aspiration Biopsy and on-Site Assessment by Pathologists for Thyroid Micronodules.

Objective: Ultrasound-guided fine-needle aspiration biopsy (US-FNAB) is a safe and effective method for screening malignant thyroid nodules. The purpose of this study was to compare the diagnostic effectiveness of US-FNAB for nodules of different sizes. Methods: A total of 1085 patients with thyroid nodules who underwent US-FNAB between January 2021 and July 2023 were included in the study. The patients were divided into three groups based on the maximum diameter of the nodules: there were 324 patients with thyroid nodules ≤5 mm in Group A, 537 patients with thyroid nodules between 6 mm and 10 mm in Group B, and 224 patients with thyroid nodules >10 mm in Group C. The US-FNAB satisfactory specimen rate, biopsy time and cytopathological results for the three groups were collected and compared with the postoperative pathological results. Results: The US-FNAB satisfactory specimen rates for Groups A, B and C were 84.57% (274/324), 90.13% (484/537) and 94.64% (212/224), respectively. The average biopsy times for Groups A, B, and C were 100.84 ± 41.58 s, 91.20 ± 32.53 s, and 79.01 ± 29.62 s, respectively. In Groups A, B, and C, 103, 192 and 73 patients, respectively, underwent surgery, and the malignancy rates were 88.35%, 85.42% and 72.6%, respectively. The sensitivity, specificity, positive predictive value, and negative predictive value of US-FNAB in Group A were 78.26%, 81.82%, 97.30%, 31.03%; respectively; those in Group B were 73.78%,85.71%,96.80%, and 35.82%, respectively; and those in Group C were 75.47%, 85.00%, 93.02% and 56.67%, respectively. Conclusion: The US-FNAB satisfactory specimen rate for thyroid nodules ≤5 mm was relatively low, but the size of nodules had no effect on the diagnostic sensitivity of US-FNAB; additionally, nodules ≤5 mm had a higher probability of malignancy. Therefore, it is necessary to perform US-FNAB for thyroid nodules with a diameter ≤5 mm with malignant signs.

A Bispecific Modeling Framework Enables the Prediction of Efficacy, Toxicity, and Optimal Molecular Design of Bispecific Antibodies Targeting MerTK.

Inhibiting MerTK on macrophages is a promising therapeutic strategy for augmenting anti-tumor immunity. However, blocking MerTK on retinal pigment epithelial cells (RPEs) results in retinal toxicity. Bispecific antibodies (bsAbs) containing an anti-MerTK therapeutic and anti-PD-L1 targeting arm were developed to reduce drug binding to MerTK on RPEs, since PD-L1 is overexpressed on macrophages but not RPEs. In this study, we present a modeling framework using in vitro receptor occupancy (RO) and pharmacokinetics (PK) data to predict efficacy, toxicity, and therapeutic index (TI) of anti-MerTK bsAbs. We first used simulations and in vitro RO data of anti-MerTK monospecific antibody (msAb) to estimate the required MerTK RO for in vivo efficacy and toxicity. Using these estimated RO thresholds, we employed our model to predict the efficacious and toxic doses for anti-MerTK bsAbs with varying affinities for MerTK. Our model predicted the highest TI for the anti-MerTK/PD-L1 bsAb with an attenuated MerTK binding arm, which was consistent with in vivo efficacy and toxicity observations. Subsequently, we used the model, in combination with sensitivity analysis and parameter scans, to suggest an optimal molecular design of anti-MerTK bsAb with the highest predicted TI in humans. Our prediction revealed that this optimized anti-MerTK bsAb should contain a MerTK therapeutic arm with relatively low affinity, along with a high affinity targeting arm that can bind to a low abundance target with slow turnover rate. Overall, these results demonstrated that our modeling framework can guide the rational design of bsAbs.

The Value of Immunocytochemical Staining for the HPV E7 Protein in the Diagnosis of Cervical Lesions.

Purpose: To investigate the value of immunocytochemical (ICC) staining for human papillomavirus (HPV) E7 protein (E7-ICC staining) as a new-generation immunological method in the cytological diagnosis of cervical lesions. Methods: The exfoliated cervical cell samples of 690 women were subjected to a liquid-based cytology test (LCT), high-risk HPV (HR-HPV) test, E7-ICC staining, and cervical biopsy for pathological diagnosis. Results: E7-ICC staining as a preliminary screening scheme for cervical precancerous lesions was comparable to the HR-HPV test in sensitivity and to the LCT in specificity. E7-ICC staining was advantageous in facilitating the secondary triage of HR-HPV-positive patients; therefore, this method can be used as an auxiliary scheme to routine LCT for diagnostic grading to improve the accuracy of cervical cytology. Conclusion: E7-ICC staining as a primary or auxiliary cytological screening scheme can effectively reduce the colposcopy referral rate.

Synchronous primary duodenal papillary adenocarcinoma and gallbladder carcinoma: A case report and review of literature.

BACKGROUND: Synchronous primary cancers (SPCs) have become increasingly frequent over the past decade. However, the coexistence of duodenal papillary and gallbladder cancers is rare, and such cases have not been previously reported in the English literature. Here, we describe an SPC case with duodenal papilla and gallbladder cancers and its diagnosis and successful management. CASE SUMMARY: A 68-year-old Chinese man was admitted to our hospital with the chief complaint of dyspepsia for the past month. Contrast-enhanced computed tomography of the abdomen performed at the local hospital revealed dilatation of the bile and pancreatic ducts and a space-occupying lesion in the duodenal papilla. Endoscopy revealed a tumor protruding from the duodenal papilla. Pathological findings for the biopsied tissue revealed tubular villous growth with moderate heterogeneous hyperplasia. Surgical treatment was selected. Macroscopic examination of this surgical specimen revealed a 2-cm papillary tumor and another tumor protruding by 0.5 cm in the gallbladder neck duct. Intraoperative rapid pathology identified adenocarcinoma in the gallbladder neck duct and tubular villous adenoma with high-grade intraepithelial neoplasia and local canceration in the duodenal papilla. After an uneventful postoperative recovery, the patient was discharged without complications. CONCLUSION: It is essential for clinicians and pathologists to maintain a high degree of suspicion while evaluating such synchronous cancers.

CLEC5a-directed bispecific antibody for effective cellular phagocytosis.

While antibody-dependent cellular phagocytosis mediated by activating Fcγ receptor is a key mechanism underlying many antibody drugs, their full therapeutic activities can be restricted by the inhibitory Fcγ receptor IIB (FcγRIIB). Here, we describe a bispecific antibody approach that harnesses phagocytic receptor CLEC5A (C-type Lectin Domain Containing 5A) to drive Fcγ receptor-independent phagocytosis, potentially circumventing the negative impact of FcγRIIB. First, we established the effectiveness of such an approach by constructing bispecific antibodies that simultaneously target CLEC5A and live B cells. Furthermore, we demonstrated its in vivo application for regulatory T cell depletion and subsequent tumor regression.

Indoleamine 2,3-dioxygenase in lung dendritic cells promotes Th2 responses and allergic inflammation.

Indoleamine 2,3 dioxygenase (IDO) has emerged as an important mediator of immune tolerance via inhibition of Th1 responses. However, the role of IDO in antigen-induced tolerance or allergic inflammation in the airways that is regulated by Th2 responses has not been elucidated. By using IDO(-/-) mice, we found no impairment of airway tolerance, but, surprisingly, absence of IDO provided significant relief from establishment of allergic airways disease, as evident from attenuated Th2 cytokine production, airway inflammation, mucus secretion, airway hyperresponsiveness, and serum ovalbumin-specific IgE. Myeloid dendritic cells isolated from lung-draining lymph nodes of mice immunized for either Th1 or Th2 response revealed fewer mature dendritic cells in the lymph nodes of IDO(-/-) mice. However, the net functional impact of IDO deficiency on antigen-induced responses was more remarkable in the Th2 model than in the Th1 model. Collectively, these data suggest that IDO is not required for the induction of immune tolerance in the airways but plays a role in promoting Th2-mediated allergic airway inflammation via unique effects on lung dendritic cells.

miR-196a-2 Promotes Malignant Progression of Thyroid Carcinoma by Targeting NRXN1.

Thyroid cancer (TC) is the most common endocrine malignant disease with a rising morbidity year by year. Accumulating studies have shown that microRNAs (miRNAs) play a regulatory role in the progression of various tumors, but the molecular regulatory mechanism of miR-196a-2 in TC is still unknown. qRT-PCR was employed to measure the expression of miR-196a-2 and NRXN1 mRNA in TC cells, while western blot was used to detect the protein expression of NRXN1. CCK-8, colony formation and flow cytometry assays were used to measure cell proliferation and apoptosis of TC cells. Dual-luciferase reporter gene assay was used to predict and verify the targeted binding relationship between miR-196a-2 and NRXN1. Our study results manifested that miR-196a-2 was dramatically overexpressed in cells of TC, while NRXN1 was lowly expressed. miR-196a-2 could promote cell proliferation and inhibit cell apoptosis of TC. Additionally, miR-196a-2 could also target and inhibit the expression of NRXN1. Silencing NRXN1 could reverse the inhibitory effect of miR-196a-2 downregulation on cell proliferation of TC, as well as the promoting effect on cell apoptosis. In a conclusion, we found that miR-196a-2 could promote cell proliferation and inhibit cell apoptosis of TC by targeting NRXN1. Therefore, miR-196a-2/NRXN1 is potential to be a molecular therapeutic target for TC.

Metabolic reprogramming of human CD8+ memory T cells through loss of SIRT1.

The expansion of CD8+CD28- T cells, a population of terminally differentiated memory T cells, is one of the most consistent immunological changes in humans during aging. CD8+CD28- T cells are highly cytotoxic, and their frequency is linked to many age-related diseases. As they do not accumulate in mice, many of the molecular mechanisms regulating their fate and function remain unclear. In this paper, we find that human CD8+CD28- T cells, under resting conditions, have an enhanced capacity to use glycolysis, a function linked to decreased expression of the NAD+-dependent protein deacetylase SIRT1. Global gene expression profiling identified the transcription factor FoxO1 as a SIRT1 target involved in transcriptional reprogramming of CD8+CD28- T cells. FoxO1 is proteasomally degraded in SIRT1-deficient CD8+CD28- T cells, and inhibiting its activity in resting CD8+CD28+ T cells enhanced glycolytic capacity and granzyme B production as in CD8+CD28- T cells. These data identify the evolutionarily conserved SIRT1-FoxO1 axis as a regulator of resting CD8+ memory T cell metabolism and activity in humans.

Fumigaclavine C, an fungal metabolite, improves experimental colitis in mice via downregulating Th1 cytokine production and matrix metalloproteinase activity.

In the present paper, the effect of Fumigaclavine C, a fungal metabolite, on experimental colitis was examined. Fumigaclavine C, when administered intraperitoneally once a day, significantly reduced the weight loss and mortality rate of mice with experimental colitis induced by intrarectally injection of 2, 4, 6-trinitrobenzene sulfonic acid (TNBS). This compound also markedly alleviated the macroscopic and microscopic appearances of colitis. Furthermore, Fumigaclavine C, given both in vivo and in vitro, showed a marked inhibition on the expression of several inflammatory cytokines, including IL-1beta, IL-2, IL-12alpha, IFN-gamma, TNF-alpha as well as MMP-9 in sacral lymph node cells, colonic patch lymphocytes and colitis tissues from the TNBS colitis mice. Meanwhile, the compound caused a dose-dependent reduction in IL-2 and IFN-gamma from the lymphocytes at the protein level and MMP-9 activity. These results suggest that Fumigaclavine C may alleviate experimental colitis mainly via down-regulating the production of Th1 cytokines and the activity of matrix metalloproteinase.

SIRT1 deacetylates RORγt and enhances Th17 cell generation.

The balance of effector and regulatory T cell function, dependent on multiple signals and epigenetic regulators, is critical to immune self-tolerance. Dysregulation of T helper 17 (Th17) effector cells is associated with multiple autoimmune diseases, including multiple sclerosis. Here, we report that Sirtuin 1 (SIRT1), a protein deacetylase previously reported to have an antiinflammatory function, in fact promotes autoimmunity by deacetylating RORγt, the signature transcription factor of Th17 cells. SIRT1 increases RORγt transcriptional activity, enhancing Th17 cell generation and function. Both T cell-specific Sirt1 deletion and treatment with pharmacologic SIRT1 inhibitors suppress Th17 differentiation and are protective in a mouse model of multiple sclerosis. Moreover, analysis of infiltrating cell populations during disease induction in mixed hematopoietic chimeras shows a marked bias against Sirt1-deficient Th17 cells. These findings reveal an unexpected proinflammatory role of SIRT1 and, importantly, support the possible therapeutic use of SIRT1 inhibitors against autoimmunity.

Disruption of chaperone-mediated autophagy-dependent degradation of MEF2A by oxidative stress-induced lysosome destabilization.

Oxidative stress has been implicated in both normal aging and various neurodegenerative disorders and it may be a major cause of neuronal death. Chaperone-mediated autophagy (CMA) targets selective cytoplasmic proteins for degradation by lysosomes and protects neurons against various extracellular stimuli including oxidative stress. MEF2A (myocyte enhancer factor 2A), a key transcription factor, protects primary neurons from oxidative stress-induced cell damage. However, the precise mechanisms of how the protein stability and the transcriptional activity of MEF2A are regulated under oxidative stress remain unknown. In this study, we report that MEF2A is physiologically degraded through the CMA pathway. In pathological conditions, mild oxidative stress (200 µM H 2O 2) enhances the degradation of MEF2A as well as its activity, whereas excessive oxidative stress (> 400 µM H 2O 2) disrupts its degradation process and leads to the accumulation of nonfunctional MEF2A. Under excessive oxidative stress, an N-terminal HDAC4 (histone deacetylase 4) cleavage product (HDAC4-NT), is significantly induced by lysosomal serine proteases released from ruptured lysosomes in a PRKACA (protein kinase, cAMP-dependent, catalytic, α)-independent manner. The production of HDAC4-NT, as a MEF2 repressor, may account for the reduced DNA-binding and transcriptional activity of MEF2A. Our work provides reliable evidence for the first time that MEF2A is targeted to lysosomes for CMA degradation; oxidative stress-induced lysosome destabilization leads to the disruption of MEF2A degradation as well as the dysregulation of its function. These findings may shed light on the underlying mechanisms of pathogenic processes of neuronal damage in various neurodegenerative-related diseases.

Rapid host defense against Aspergillus fumigatus involves alveolar macrophages with a predominance of alternatively activated phenotype.

The ubiquitous fungus Aspergillus fumigatus is associated with chronic diseases such as invasive pulmonary aspergillosis in immunosuppressed patients and allergic bronchopulmonary aspergillosis (ABPA) in patients with cystic fibrosis or severe asthma. Because of constant exposure to this fungus, it is critical for the host to exercise an immediate and decisive immune response to clear fungal spores to ward off disease. In this study, we observed that rapidly after infection by A. fumigatus, alveolar macrophages predominantly express Arginase 1 (Arg1), a key marker of alternatively activated macrophages (AAMs). The macrophages were also found to express Ym1 and CD206 that are also expressed by AAMs but not NOS2, which is expressed by classically activated macrophages. The expression of Arg1 was reduced in the absence of the known signaling axis, IL-4Rα/STAT6, for AAM development. While both Dectin-1 and TLR expressed on the cell surface have been shown to sense A. fumigatus, fungus-induced Arg1 expression in CD11c(+) alveolar macrophages was not dependent on either Dectin-1 or the adaptor MyD88 that mediates intracellular signaling by most TLRs. Alveolar macrophages from WT mice efficiently phagocytosed fungal conidia, but those from mice deficient in Dectin-1 showed impaired fungal uptake. Depletion of macrophages with clodronate-filled liposomes increased fungal burden in infected mice. Collectively, our studies suggest that alveolar macrophages, which predominantly acquire an AAM phenotype following A. fumigatus infection, have a protective role in defense against this fungus.

Activation of c-Kit in dendritic cells regulates T helper cell differentiation and allergic asthma.

Dendritic cells (DCs) are integral to the differentiation of T helper cells into T helper type 1 T(H)1, T(H)2 and T(H)17 subsets. Interleukin-6 (IL-6) plays an important part in regulating these three arms of the immune response by limiting the T(H)1 response and promoting the T(H)2 and T(H)17 responses. In this study, we investigated pathways in DCs that promote IL-6 production. We show that the allergen house dust mite (HDM) or the mucosal adjuvant cholera toxin promotes cell surface expression of c-Kit and its ligand, stem cell factor (SCF), on DCs. This dual upregulation of c-Kit and SCF results in sustained signaling downstream of c-Kit, promoting IL-6 secretion. Intranasal administration of antigen into c-Kit-mutant mice or neutralization of IL-6 in cultures established from the lung-draining lymph nodes of immunized wild-type mice blunted the T(H)2 and T(H)17 responses. DCs lacking functional c-Kit or those unable to express membrane-bound SCF secreted lower amounts of IL-6 in response to HDM or cholera toxin. DCs expressing nonfunctional c-Kit were unable to induce a robust T(H)2 or T(H)17 response and elicited diminished allergic airway inflammation when adoptively transferred into mice. Expression of the Notch ligand Jagged-2, which has been associated with T(H)2 differentiation, was blunted in DCs from c-Kit-mutant mice. c-Kit upregulation was specifically induced by T(H)2- and T(H)17-skewing stimuli, as the T(H)1-inducing adjuvant, CpG oligodeoxynucleotide, did not promote either c-Kit or Jagged-2 expression. DCs generated from mice expressing a catalytically inactive form of the p110delta subunit of phosphatidylinositol-3 (PI3) kinase (p110(D910A)) secreted lower amounts of IL-6 upon stimulation with cholera toxin. Collectively, these results highlight the importance of the c-Kit-PI3 kinase-IL-6 signaling axis in DCs in regulating T cell responses.