Stromal cell diversity associated with immune evasion in human triple-negative breast cancer.

The tumour stroma regulates nearly all stages of carcinogenesis. Stromal heterogeneity in human triple-negative breast cancers (TNBCs) remains poorly understood, limiting the development of stromal-targeted therapies. Single-cell RNA sequencing of five TNBCs revealed two cancer-associated fibroblast (CAF) and two perivascular-like (PVL) subpopulations. CAFs clustered into two states: the first with features of myofibroblasts and the second characterised by high expression of growth factors and immunomodulatory molecules. PVL cells clustered into two states consistent with a differentiated and immature phenotype. We showed that these stromal states have distinct morphologies, spatial relationships and functional properties in regulating the extracellular matrix. Using cell signalling predictions, we provide evidence that stromal-immune crosstalk acts via a diverse array of immunoregulatory molecules. Importantly, the investigation of gene signatures from inflammatory-CAFs and differentiated-PVL cells in independent TNBC patient cohorts revealed strong associations with cytotoxic T-cell dysfunction and exclusion, respectively. Such insights present promising candidates to further investigate for new therapeutic strategies in the treatment of TNBCs.

Regulatory T cells prevent inducible BALT formation by dampening neutrophilic inflammation.

Inducible BALT (iBALT) can amplify pulmonary or systemic inflammatory responses to the benefit or detriment of the host. We took advantage of the age-dependent formation of iBALT to interrogate the underlying mechanisms that give rise to this ectopic, tertiary lymphoid organ. In this study, we show that the reduced propensity for weanling as compared with neonatal mice to form iBALT in response to acute LPS exposure is associated with greater regulatory T cell expansion in the mediastinal lymph nodes. Ab- or transgene-mediated depletion of regulatory T cells in weanling mice upregulated the expression of IL-17A and CXCL9 in the lungs, induced a tissue neutrophilia, and increased the frequency of iBALT to that observed in neonatal mice. Remarkably, neutrophil depletion in neonatal mice decreased the expression of the B cell active cytokines, a proliferation-inducing ligand and IL-21, and attenuated LPS-induced iBALT formation. Taken together, our data implicate a role for neutrophils in lymphoid neogenesis. Neutrophilic inflammation is a common feature of many autoimmune diseases in which iBALT are present and pathogenic, and hence the targeting of neutrophils or their byproducts may serve to ameliorate detrimental lymphoid neogenesis in a variety of disease contexts.

Toll/IL-1 signaling is critical for house dust mite-specific helper T cell type 2 and type 17 [corrected] responses.

RATIONALE: One of the immunopathological features of allergic inflammation is the infiltration of helper T type 2 (Th2) cells to the site of disease. Activation of innate pattern recognition receptors such as Toll-like receptors (TLRs) plays a critical role in helper T type 1 cell differentiation, yet their contribution to the generation of Th2 responses to clinically relevant aeroallergens remains poorly defined. OBJECTIVES: To determine the requirement for TLR2, TLR4, and the Toll/IL-1 receptor domain adaptor protein MyD88 in a murine model of allergic asthma. METHODS: Wild-type and factor-deficient ((-/-)) mice were sensitized intranasally to the common allergen house dust mite (HDM) and challenged 2 weeks later on four consecutive days. Measurements of allergic airway inflammation, T-cell cytokine production, and airway hyperreactivity were performed 24 hours later. MEASUREMENTS AND MAIN RESULTS: Mice deficient in MyD88 were protected from the cardinal features of allergic asthma, including granulocytic inflammation, Th2 cytokine production and airway hyperreactivity. Although HDM activated NF-kappaB in TLR2- or TLR4-expressing HEK cells, only in TLR4(-/-) mice was the magnitude of allergic airway inflammation and hyperreactivity attenuated. The diminished Th2 response present in MyD88(-/-) and TLR4(-/-) mice was associated with fewer OX40 ligand-expressing myeloid dendritic cells in the draining lymph nodes during allergic sensitization. Finally, HDM-specific IL-17 production and airway neutrophilia were attenuated in MyD88(-/-) but not TLR4(-/-) mice. CONCLUSIONS: Together, these data suggest that Th2- and Th17-mediated inflammation generated on inhalational HDM exposure is differentially regulated by the presence of microbial products and the activation of distinct MyD88-dependent pattern recognition receptors.

Chlamydia muridarum infection subverts dendritic cell function to promote Th2 immunity and airways hyperreactivity.

There is strong epidemiological evidence that Chlamydia infection can lead to exacerbation of asthma. However, the mechanism(s) whereby chlamydial infection, which normally elicits a strong Th type 1 (Th1) immune response, can exacerbate asthma, a disease characterized by dominant Th type 2 (Th2) immune responses, remains unclear. In the present study, we show that Chlamydia muridarum infection of murine bone marrow-derived dendritic cells (BMDC) modulates the phenotype, cytokine secretion profile, and Ag-presenting capability of these BMDC. Chlamydia-infected BMDC express lower levels of CD80 and increased CD86 compared with noninfected BMDC. When infected with Chlamydia, BMDC secrete increased TNF-alpha, IL-6, IL-10, IL-12, and IL-13. OVA peptide-pulsed infected BMDC induced significant proliferation of transgenic CD4(+) DO11.10 (D10) T cells, strongly inhibited IFN-gamma secretion by D10 cells, and promoted a Th2 phenotype. Intratracheal transfer of infected, but not control noninfected, OVA peptide-pulsed BMDC to naive BALB/c mice, which had been i.v. infused with naive D10 T cells, resulted in increased levels of IL-10 and IL-13 in bronchoalveolar lavage fluid. Recipients of these infected BMDC showed significant increases in airways resistance and decreased airways compliance compared with mice that had received noninfected BMDC, indicative of the development of airways hyperreactivity. Collectively, these data suggest that Chlamydia infection of DCs allows the pathogen to deviate the induced immune response from a protective Th1 to a nonprotective Th2 response that could permit ongoing chronic infection. In the setting of allergic airways inflammation, this infection may then contribute to exacerbation of the asthmatic phenotype.

The contribution of toll-like receptors to the pathogenesis of asthma.

Asthma is a major disease in the westernized world and its incidence has significantly increased over the past 40 years. Our understanding of the pathogenesis of asthma remains rudimentary, and for this reason, little has been accomplished by way of targeted intervention, either at a population level (to reduce the overall prevalence) or at an individual level (to treat the cause). Instead, the management strategy currently in use relies on broad-spectrum anti-inflammatory agents, generally glucocorticoids and long-acting beta2 agonists. The recent discovery of toll-like receptors (TLRs), with their role as the initiators of the innate immune response and inflammation, suggests that modulating these receptors may be beneficial in the treatment of allergic disorders. We review here the cellular distribution of TLR in the lung and their potential contribution to the processes that promote T helper 2 (Th2) immunity and infection-induced exacerbations of allergic lung disease.

Eosinophils contribute to innate antiviral immunity and promote clearance of respiratory syncytial virus.

Eosinophils are recruited to the lungs in response to respiratory syncytial virus (RSV) infection; however, their role in promoting antiviral host defense remains unclear. Here, we demonstrate that eosinophils express TLRs that recognize viral nucleic acids, are activated and degranulate after single-stranded RNA (ssRNA) stimulation of the TLR-7-MyD88 pathway, and provide host defense against RSV that is MyD88 dependent. In contrast to wild-type mice, virus clearance from lung tissue was more rapid in hypereosinophilic (interleukin-5 transgenic) mice. Transfer of wild-type but not MyD88-deficient eosinophils to the lungs of RSV-infected wild-type mice accelerated virus clearance and inhibited the development of airways hyperreactivity. Similar responses were observed when infected recipient mice were MyD88 deficient. Eosinophils isolated from infected hypereosinophilic MyD88-sufficient but not MyD88-deficient mice expressed greater amounts of IFN regulatory factor (IRF)-7 and eosinophil-associated ribonucleases EAR-1 and EAR-2. Hypereosinophilia in the airways of infected mice also correlated with increased expression of IRF-7, IFN-beta, and NOS-2, and inhibition of NO production with the NOS-2 inhibitor L-NMA partially reversed the accelerated virus clearance promoted by eosinophils. Collectively, our results demonstrate that eosinophils can protect against RSV in vivo, as they promote virus clearance and may thus limit virus-induced lung dysfunction.