Search

BackgroundSolitary chemosensory cells (SCCs) are rare epithelial cells enriched in nasal polyps and are the primary source of interleukin-25 (IL-25), an innate cytokine eliciting T-helper 2 (Th2) immune response. Although it is proposed that SCCs are stimulated by antigens released by upper airway pathogens, the exogenous triggers of human SCCs remain elusive. We studied patients with noninvasive fungal rhinosinusitis to determine whether extracts of Aspergillus fumigatus and Alternaria alternata stimulate SCC proliferation as an early event in type 2 inflammation.MethodsMulticolor flow cytometry, immunofluorescence, and enzyme-linked immunoassay were used to interrogate mucosa from patients with mycetomas and allergic fungal rhinosinusitis (AFRS) for SCCs and IL-25. Primary sinonasal epithelial cells from AFRS patients and noninflamed inferior turbinates were stimulated with fungal extracts for 72 hours, and SCC population frequency as well as mitotic activity were quantified using flow cytometry.ResultsSCCs producing IL-25 are enriched in inflamed mucosa compared with intrapatient noninflamed control tissue (38.6% vs 6.5%, p = 0.029). In cultured sinonasal epithelial cells from AFRS nasal polyps, Aspergillus fumigatus and Alternaria alternata stimulated higher SCC frequency compared with controls (27.4% vs 10.6%, p = 0.002; 18.1% vs 10.6%, p = 0.046), which led to increased IL-25 secretion in culture media (75.5 vs 3.3 pg/mL, p < 0.001; 32.3 vs 3.3 pg/mL, p = 0.007). Ki-67 expression was higher in SCCs grown in fungal stimulation conditions compared with controls.ConclusionAlthough fungal antigens are known to potentiate immune response through innate cytokines, including IL-25, the early expansion of SCCs in the presence of fungus has not been described. This early event in the pathogenesis of noninvasive fungal rhinosinusitis may represent a target for intervention.

Coordinated efforts between macrophages and epithelia are considered essential for wound healing, but the macrophage-derived molecules responsible for repair are poorly defined. This work demonstrates that lung macrophages rely upon Trefoil factor 2 to promote epithelial proliferation following damage caused by sterile wounding, Nippostrongylus brasiliensis or Bleomycin sulfate. Unexpectedly, the presence of T, B, or ILC populations was not essential for macrophage-driven repair. Instead, conditional deletion of TFF2 in myeloid-restricted CD11cCre TFF2 flox mice exacerbated lung pathology and reduced the proliferative expansion of CD45- EpCAM+ pro-SPC+ alveolar type 2 cells. TFF2 deficient macrophages had reduced expression of the Wnt genes Wnt4 and Wnt16 and reconstitution of hookworm-infected CD11cCre TFF2flox mice with rWnt4 and rWnt16 restored the proliferative defect in lung epithelia post-injury. These data reveal a previously unrecognized mechanism wherein lung myeloid phagocytes utilize a TFF2/Wnt axis as a mechanism that drives epithelial proliferation following lung injury.

Chronic rhinosinusitis with nasal polyps (CRSwNP) is commonly characterized by type-2 inflammation. It is established that group-2 innate lymphoid cells (ILC2s) are a subset of immune cells important in orchestrating mucosal type-2 response. IL-25 is an epithelial-derived cytokine that is a critical activator of ILC2s. Recent evidence demonstrates that specialized taster epithelial cells, such as solitary chemosensory cells (SCCs), may be producers of IL-25. To elucidate the relationship between SCCs and ILC2s in CRSwNP, we sought to quantify ILC2s and SCCs to determine if these cell types are enriched in nasal polyps compared to healthy sinonasal mucosa. We quantified SCCs and ILC2s using multicolor flow cytometry in nasal polyps and non-inflamed turbinate mucosa from seven patients and investigated the role of IL-13 and dexamethasone on SCC frequency using tissue explants of nasal polyps and turbinate mucosa. SCCs were found to be the primary source of IL-25. Nasal polyps demonstrated higher populations of SCCs (33.0% vs 5.6%, p < 0.001) and ILC2s (2.40% vs 0.19%, p = 0.008) compared to patient-matched nonpolypoid turbinates. In cultured polyp explants, exogenous IL-13 increased the proportion of epithelial SCCs (40.2% IL-13 condition vs 28.9% untreated, p = 0.012), and this effect was reversed by addition of dexamethasone (40.2% vs 8.9%, p < 0.0005). These data support SCC and ILC2 expansion as well as increased IL-25 production in nasal polyps and may represent early events in the pathogenesis of CRSwNP. IL-13 stimulates proliferation of SCC in a feed-forward loop, a process that is steroid-sensitive.

Schistosoma haematobium is the etiologic agent for urogenital schistosomiasis, a major source of morbidity and mortality for more than 112 million people worldwide. Infection with S. haematobium results in a variety of immunopathologic sequelae caused by parasite oviposition within the urinary tract, which drives inflammation, hematuria, fibrosis, bladder dysfunction, and increased susceptibility to urothelial carcinoma. While humans readily develop urogenital schistosomiasis, the lack of an experimentally-tractable model has greatly impaired our understanding of the mechanisms that underlie this important disease. We have developed an improved mouse model of S. haematobium urinary tract infection that recapitulates several aspects of human urogenital schistosomiasis. Following microinjection of purified S. haematobium eggs into the bladder wall, mice consistently develop macrophage-rich granulomata that persist for at least 3 months and pass eggs in their urine. Importantly, egg-injected mice also develop urinary tract fibrosis, bladder dysfunction, and various urothelial changes morphologically reminiscent of human urogenital schistosomiasis. As expected, S. haematobium egg-induced immune responses in the immediate microenvironment, draining lymph nodes, and systemic circulation are associated with a Type 2-dominant inflammatory response, characterized by high levels of interleukin-4, eosinophils, and IgE. Taken together, our novel mouse model may help facilitate a better understanding of the unique pathophysiological mechanisms of epithelial dysfunction, tissue fibrosis, and oncogenesis associated with urogenital schistosomiasis.

Th2 cells drive protective immunity against most parasitic helminths, but few mechanisms have been demonstrated that facilitate pathogen clearance. We show that IL-4 and IL-13 protect against intestinal lumen-dwelling worms primarily by inducing intestinal epithelial cells (IECs) to differentiate into goblet cells that secrete resistin-like molecule (RELM) beta. RELM-beta is essential for normal spontaneous expulsion and IL-4-induced expulsion of Nippostrongylus brasiliensis and Heligmosomoides polygyrus, which both live in the intestinal lumen, but it does not contribute to immunity against Trichinella spiralis, which lives within IEC. RELM-beta is nontoxic for H. polygyrus in vitro but directly inhibits the ability of worms to feed on host tissues during infection. This decreases H. polygyrus adenosine triphosphate content and fecundity. Importantly, RELM-beta-driven immunity does not require T or B cells, alternative macrophage activation, or increased gut permeability. Thus, we demonstrate a novel mechanism for host protection at the mucosal interface that explains how stimulation of epithelial cells by IL-4 and IL-13 contributes to protection against parasitic helminthes that dwell in the intestinal lumen.

Th2 cells drive protective immunity against most parasitic helminths, but few mechanisms have been demonstrated that facilitate pathogen clearance. We show that IL-4 and IL-13 protect against intestinal lumen-dwelling worms primarily by inducing intestinal epithelial cells (IECs) to differentiate into goblet cells that secrete resistin-like molecule (RELM) beta. RELM-beta is essential for normal spontaneous expulsion and IL-4-induced expulsion of Nippostrongylus brasiliensis and Heligmosomoides polygyrus, which both live in the intestinal lumen, but it does not contribute to immunity against Trichinella spiralis, which lives within IEC. RELM-beta is nontoxic for H. polygyrus in vitro but directly inhibits the ability of worms to feed on host tissues during infection. This decreases H. polygyrus adenosine triphosphate content and fecundity. Importantly, RELM-beta-driven immunity does not require T or B cells, alternative macrophage activation, or increased gut permeability. Thus, we demonstrate a novel mechanism for host protection at the mucosal interface that explains how stimulation of epithelial cells by IL-4 and IL-13 contributes to protection against parasitic helminthes that dwell in the intestinal lumen.

Host responses against metazoan parasites or an array of environmental substances elicit type 2 immunity. Despite its protective function, type 2 immunity also drives allergic diseases. The mechanisms that regulate the magnitude of the type 2 response remain largely unknown. Here, we show that genetic ablation of a receptor tyrosine kinase encoded by Tyro3 in mice or the functional neutralization of its ortholog in human dendritic cells resulted in enhanced type 2 immunity. Furthermore, the TYRO3 agonist PROS1 was induced in T cells by the quintessential type 2 cytokine, interleukin-4. T cell-specific Pros1 knockouts phenocopied the loss of Tyro3.Thus, a PROS1-mediated feedback from adaptive immunity engages a rheostat, TYRO3, on innate immune cells to limit the intensity of type 2 responses. [ABSTRACT FROM AUTHOR]