Hidradenitis suppurativa (HS) is a debilitating chronic inflammatory skin disease characterized by chronic abscess formation and development of multiple draining sinus tracts in the groin, axillae, and perineum. Using proteomic and transcriptomic approaches, we characterized the inflammatory responses in HS in depth, revealing immune responses centered on IFN-γ, IL-36, and TNF, with lesser contribution from IL-17A. We further identified B cells and plasma cells, with associated increases in immunoglobulin production and complement activation, as pivotal players in HS pathogenesis, with Bruton’s tyrosine kinase (BTK) and spleen tyrosine kinase (SYK) pathway activation as a central signal transduction network in HS. These data provide preclinical evidence to accelerate the path toward clinical trials targeting BTK and SYK signaling in moderate-to-severe HS.

Cryptococcus neoformans is a major fungal pathogen that disseminates to the central nervous system (CNS) to cause fatal meningoencephalitis, but little is known about immune responses within this immune-privileged site. CD4 ϩ T cells have demonstrated roles in anticryptococcal defenses, but increasing evidence suggests that they may contribute to clinical deterioration and pathology in both HIVpositive (HIVϩ) and non-HIV patients who develop immune reconstitution inflammatory syndrome (IRIS) and post-infectious inflammatory response syndrome (PIIRS), respectively. Here we report a novel murine model of cryptococcal meningoencephalitis and a potential damaging role of T cells in disseminated cryptococcal CNS infection. In this model, fungal burdens plateaued in the infected brain by day 7 postinfection, but activation of microglia and accumulation of CD45 hi leukocytes was significantly delayed relative to fungal growth and did not peak until day 21. The inflammatory leukocyte infiltrate consisted predominantly of gamma interferon (IFN-␥)-producing CD4 ϩ T cells, conventionally believed to promote fungal clearance and recovery. However, more than 50% of mice succumbed to infection and neurological dysfunction between days 21 and 35 despite a 100-fold reduction in fungal burdens. Depletion of CD4 ϩ cells significantly impaired IFN-␥ production, CD8 ϩ T cell and myeloid cell accumulation, and fungal clearance from the CNS but prevented the development of clinical symptoms and mortality. These findings conclusively demonstrate that although CD4 ϩ T cells are necessary to control fungal growth, they can also promote significant immunopathology and mortality during CNS infection. The results from this model may provide important guidance for development and use of anti-inflammatory therapies to minimize CNS injury in patients with severe cryptococcal infections.IMPORTANCE CNS infection with the fungal pathogen Cryptococcus neoformans often results in debilitating brain injury and has a high mortality rate despite antifungal treatment. Treatment is complicated by the fact that immune responses needed to eliminate infection are also thought to drive CNS damage in a subset of both HIVϩ and non-HIV patients. Thus, physicians need to balance efforts to enhance patients' immune responses and promote microbiological control with antiinflammatory therapy to protect the CNS. Here we report a novel model of cryptococcal meningoencephalitis demonstrating that fungal growth within the CNS does not immediately cause symptomatic disease. Rather, accumulation of antifungal immune cells critically mediates CNS injury and mortality. This model demonstrates that antifungal immune responses in the CNS can cause detrimental pathology and

The sequences presented in this article have been submitted to the Gene Expression Omnibus (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE124939) under accession number GSE124939.

Cryptococcus neoformans is a ubiquitous, opportunistic fungal pathogen but the cell signaling pathways that drive T cell responses regulating anti-fungal immunity are incompletely understood. Notch is a key signaling pathway regulating T cell development, and differentiation and functional responses of mature T cells in the periphery. Targeting of Notch signaling within T cells has been proposed as potential treatment for alloimmune and autoimmune disorders, but it is unknown whether disturbances to T cell immunity may render these patients vulnerable to fungal infections. To elucidate the role of Notch signaling during fungal infections, we infected mice expressing the pan-Notch inhibitor dominant negative Mastermind-like (DNMAML) within mature T cells with C. neoformans. Inhibition of T cell restricted Notch signaling increased fungal burdens in the lungs and CNS, diminished pulmonary leukocyte recruitment and simultaneously impaired Th1 and Th2 responses. Pulmonary leukocyte cultures from T cell Notch-deprived mice produced less IFN-γ, IL-5 and IL-13 than WT cells. This correlated with lower frequencies of IFN-γ, IL-5 and IL-13 producing CD4+ T cells; reduced expression of Th1 and Th2 associated transcription factors, Tbet and Gata3; and reduced production of IFN-γ by CD8+ T cells. In contrast, Th17 responses were largely unaffected by Notch signaling. The changes in T cell responses corresponded with impaired macrophage activation and reduced leukocyte accumulation, leading to diminished fungal control. These results identify Notch signaling as a previously unappreciated regulator of Th1 and Th2 immunity and an important element of antifungal defenses against cryptococcal infection and CNS dissemination.

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The immunopathogenesis of psoriasis, a common chronic inflammatory disease of the skin, is incompletely understood. Here we demonstrate, using a combination of single cell and spatial RNA sequencing, IL-36 dependent amplification of IL-17A and TNF inflammatory responses in the absence of neutrophil proteases, which primarily occur within the supraspinous layer of the psoriatic epidermis. We further show that a subset of SFRP2+ fibroblasts in psoriasis contribute to amplification of the immune network through transition to a pro-inflammatory state. The SFRP2+ fibroblast communication network involves production of CCL13, CCL19 and CXCL12, connected by ligand-receptor interactions to other spatially proximate cell types: CCR2+ myeloid cells, CCR7+LAMP3+ dendritic cells, and CXCR4 expressed on both CD8+ Tc17 cells and keratinocytes, respectively. The SFRP2+ fibroblasts also express cathepsin S, further amplifying inflammatory responses by activating IL-36G in keratinocytes. These data provide an in-depth view of psoriasis pathogenesis, which expands our understanding of the critical cellular participants to include inflammatory fibroblasts and their cellular interactions.

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