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.

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 singlestranded 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) - IntroductionThere are numerous studies addressing the contribution of eosinophilic leukocytes to immune mechanisms regulating allergic diseases and granulomatous and fibrotic disorders, and eosinophil recruitment in response to helminthic parasite infection has been well documented. 1 In contrast, there is only limited information on the role of eosinophils in immunity against infectious pathogens. Eosinophil recruitment was observed in response to acute severe respiratory syncytial virus (RSV) infection in human infants, 2-4 and infection of airway epithelial cells results in the expression of several eosinophil chemoattractants. 5,6 However, it is not at all clear whether eosinophils contribute to host defense or to the immunopathology observed in response to RSV infection. RSV infection is the most commonly identified cause of lower respiratory tract infections in infants, and severe disease has been associated with progression to childhood asthma, a disease state characterized by a mild to moderate eosinophilia. 7,8 In addition, exacerbations of established asthma are most frequently caused by viral infections, of which RSV has been implicated. 9 Recently, transcripts encoding Toll-like receptor (TLR)-1, TLR-4, TLR-7, TLR-9, and TLR-10, all of which coordinate innate and acquired immune responses, were shown to be expressed constitutively by eosinophils. 10 Recognition of viral nucleic acids, including double-stranded RNA (dsRNA), single-stranded RNA (ssRNA), and dsDNA, occurs via activation of TLR-3, TLR-7, and TLR-9, respectively, and results in the production of type I IFNs and the initiation of the antiviral host response. 11-15 RSV is a negative ssRNA virus that generates dsRNA during its replication cycle. Although TLR-3 and TLR-7 both recognize viral RNA, TLR-3 uses toll-interleukin receptor domain-containing adaptorinducing IFN-␤ (TRIF) and does not require MyD88, while TLR-7 signaling is MyD88 dependent. 12 These differences in adaptor usage, along with the activation of different IFN regulatory factors (IRFs), are proposed to provi...

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.