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Cryptococcus gattii is an emerging fungal pathogen that is acquired through the respiratory tract and causes invasive infections in both immunocompromised and otherwise healthy people. Many of these apparently immunocompetent patients are subsequently found to have autoantibodies against the pleiotropic cytokine GM-CSF. In this study, we investigated the potential role of GM-CSF (or CSF2) in the host response to C. gattii using a murine model of infection. Interestingly, infected Csf2-/- mice were found to have significantly improved survival and decreased lung fungal burden compared to wild type (WT) mice. We determined that during C. gattii infection, GM-CSF promotes the differentiation of monocytes into alveolar and interstitial macrophages. When these macrophages are ablated in CCR2-DTR+ mice, there is a corresponding improvement in survival with decreased lung fungal burden, thus phenocopying Csf2-/- mice. WT bone-marrow derived macrophages challenged with C. gattii and interstitial and alveolar macrophages from infected WT mice are unable to undergo M1 polarization, suggesting that monocyte-derived macrophages (moMacs) are rendered permissive for fungal proliferation. Therefore, GM-CSF and moMacs mediate immune responses that are harmful to the host. We further found that GM-CSF and moMacs preferentially promote the influx of eosinophils over neutrophils into the infected lung which is associated with substantial inflammatory lung pathology. Ablation of neutrophils using Mrp8cretg iDTR+ mice significantly increased C. gattii burden in the lungs, indicating that GM-CSF and moMacs block the entry of these beneficial, fungal-clearing granulocytes during infection. Altogether, our results show that GM-CSF plays a key role in impeding host anti-fungal responses to C. gattii by coordinating monocyte-derived macrophages and granulocyte activity and crosstalk. Author summaryCryptococcus gattii is an environmental fungus that can cause severe lung and brain infections after inhalation through the respiratory tract. C. gattii causes disease in patients with known immune deficits but also in individuals that are apparently healthy. Studies on otherwise healthy people who become infected with C. gattii suggest that they may have a previously unrecognized problem involving granulocyte macrophage-colony stimulating factor (GM-CSF), a cytokine, or messenger protein, that is an important part of the immune system. Here, we investigate the role of GM-CSF in the immune response to C. gattii using a mouse model of infection. We find that C. gattii increases GM-CSF in the lungs, leading to the influx of immune cells, including monocyte-derived macrophages and eosinophils, while inhibiting the entry of neutrophils. The macrophages and eosinophils allow the fungus to proliferate and cause inflammatory damage to the lungs, which is ultimately fatal. The absence of neutrophils also contributes to fungal growth, as these immune cells would otherwise be able to help kill the fungus. Our study provides new insight into how GM-CSF regulates immunity to C. gattii and has important implications as to the mechanisms that govern susceptibility to this infection.

T cell dysfunction is a pivotal driving factor in autoimmune diseases, yet its underlying regulatory mechanisms remain incompletely understood. The role of long non-coding RNAs (lncRNAs) in immune regulation has gradually been recognized, although their functional mechanisms in T cells remain elusive. This study focuses on lncBADR (LncRNA Branched-chain Amino acids Degradation Regulator), elucidating its mechanism by which it regulates branched-chain amino acids (BCAAs) metabolism to influence T cell effector functions. Mice with specific knockout of lncBADR (T celllncBADR?/?) exhibited markedly ameliorated experimental autoimmune encephalomyelitis (EAE) symptoms. Mechanistic investigations revealed that lncBADR inhibits BCAAs degradation by binding to the enzymes Mccc1 and Pcca, leading to the accumulation of BCAAs within T-cells. This, in turn, activates the mTOR-Stat1 signaling pathway, promoting IFN-¦Ã secretion and exacerbating EAE pathology. In contrast, knockout of lncBADR restored BCAAs degradation, significantly reducing IFN-¦Ã secretion in T cells and suppressing their pathogenic functions. Further studies demonstrated that high-BCAAs feeding partially reversed the protective effects of lncBADR knockout, indicating that lncBADR plays a crucial role in autoimmune inflammation by regulating BCAAs metabolism. This study offers new insights into targeting lncBADR or modulating BCAAs metabolism as potential therapeutic strategies for autoimmune diseases.

The ovary is one of the first organs to exhibit signs of aging, characterized by reduced tissue function, chronic inflammation, and fibrosis. Multinucleated giant cells (MNGCs), formed by macrophage fusion, typically occur in chronic immune pathologies, including infectious and non-infectious granulomas and the foreign body response, but are also observed in the aging ovary. The function and consequence of ovarian MNGCs remain unknown as their biological activity is highly context-dependent, and their large size has limited their isolation and analysis through technologies such as single-cell RNA sequencing. In this study, we define ovarian MNGCs through a deep analysis of their presence across age and species using advanced imaging technologies as well as their unique transcriptome using laser capture microdissection. MNGCs form complex interconnected networks that increase with age in both mouse and nonhuman primate ovaries. MNGCs are characterized by high Gpnmb expression, a putative marker of ovarian and non-ovarian MNGCs. Pathway analysis highlighted functions in apoptotic cell clearance, lipid metabolism, proteolysis, immune processes, and increased oxidative phosphorylation and antioxidant activity. Thus, MNGCs have signatures related to degradative processes, immune function, and high metabolic activity. These processes were enriched in MNGCs compared to primary ovarian macrophages, suggesting discrete functionality. MNGCs express CD4 and colocalize with T-cells, which were enriched in regions of MNGCs, indicative of a close interaction between these immune cell types. These findings implicate MNGCs in modulation of the ovarian immune landscape during aging given their high penetrance and unique molecular signature that supports degradative and immune functions. Ovarian multinucleated giant cells are a unique macrophage population that arise within the aging mammalian ovary. This study characterizes their transcriptome in mice, uncovering a potential role in degradation of cellular debris and immune signaling, suggesting a potential contribution to ovarian inflammation during aging.