Neutrophil S100A9 supports M2 macrophage niche formation in granulomas

TAP-independent induction of N-myristoylated lipopeptide-specific CTLs in transgenic mice expressing the rhesus MHC class I allomorph, Mamu-B*098

A novel subset of classical major histocompatibility complex class I molecules has recently been identified in rhesus monkeys that mediates the presentation of N-myristoylated lipopeptides, rather than conventional peptides, to CD8+ cytotoxic T lymphocytes (CTLs). For example, the rhesus Mamu-B*098 allomorph binds an N-terminal 5-mer fragment (C14 fatty acid-Gly-Gly-Ala-Ile-Ser; C14nef5) derived from the N-myristoylated SIV Nef protein and activates C14nef5-specific CTLs. Additionally, a transporter for antigen presentation (TAP)-independent cell-surface expression was observed for Mamu-B*098 in the in vitro transfection experiments, leading us to hypothesize that TAP-independent pathways may exist for CTL activation. To address this directly, we generated transgenic mice expressing Mamu-B*098 and analyzed its function under TAP-deficient conditions. We first confirmed that its expression level was unchanged on the surface of TAP-deficient cells compared with that of TAP-sufficient cells. Second, the CD8+ T cell population, but not the CD4+ T cell population, increased in TAP knockout (KO) mice as a result of the acquisition of Mamu-B*098 expression. Third, C14nef5-specific, Mamu-B*098-restricted CD8+ T cells were readily inducible in Mamu-B*098 transgenic/TAP KO but not in nontransgenic/TAP KO mice. Finally, the CD8+ T cells expressed cytolytic granule contents and functioned as CTLs. These findings provide evidence that in addition to conventional peptide-specific CTL responses that require TAP, an alternative TAP-independent pathway for CTL activation exists in primates. This novel pathway may be valuable when TAP is targeted by pathogenic viruses for immune evasion. We propose that the established concept of major histocompatibility complex class I biology may require modifications to incorporate TAP-independent pathways of lipopeptide-specific CTL responses.

Targeted inhibitors of S100A9 alleviate chronic pancreatitis by inhibiting M2 macrophage polarization via the TAOK3-JNK signaling pathway

Background

Chronic pancreatitis (CP) is a fibro-inflammatory syndrome with unclear pathogenesis and futile therapy. CP's microenvironment disrupts the fine-tuned balance of macrophage polarization toward a predominance of the M2-like phenotype associated with fibrosis. S100A9 is mainly expressed in monocytes as a potent regulator of macrophage phenotype and function. Here, we investigated the S100A9-related mechanisms underlying CP pathology induced by macrophages polarization.

Methods

S100a9 knockout (S100a9 -/-) mice and an in vitro coculture system of macrophages overexpressing S100a9 and primary PSCs were constructed to investigate the effects and mechanisms of S100A9-mediated macrophage polarization on pancreatic inflammation and fibrosis underpinning CP pathology. Furthermore, a variety of S100A9-targeted small-molecule compounds were screened from U.S. Food and Drug Administration (FDA)-listed drug libraries through molecular docking and virtual screening techniques.

Results

In CP progression, S100A9 upregulation induces M2 macrophage polarization to accelerate fibrosis via thousand-and-one amino acid kinase 3 (TAOK3)-c-Jun N-terminal kinase (JNK) signaling pathway, and loss of S100A9 reduces CP injury in vitro and in vivo. Coimmunoprecipitation (co-IP) and molecular docking experiments proved that S100A9 may interact directly with TAOK3 through salt bridges and hydrogen bonding interactions of the residues in the S100A9 protein. Furthermore, cobamamide and daptomycin, as inactivators of the S100A9-TAOK3 interaction, can improve CP by inhibiting the polarization of M2 macrophages.

Conclusions

S100A9 is a significant promoter of M2-like macrophage-induced fibrosis in CP via the TAOK3-JNK signaling pathway. Cobamamide and daptomycin, targeted inhibitors of the S100A9-TAOK3 interaction, may become candidate drugs for CP immunotherapy.

Targeting S100A9 attenuates social dysfunction by modulating neuroinflammation and myelination in a mouse model of autism

Growing evidence supports a role for dysregulated neuroinflammation in autism. However, the underlying mechanisms of microglia-evoked neuroinflammation in the development of autistic phenotypes have not been elucidated. This study aimed to investigate the role and underlying mechanisms of microglial S100 calcium-binding protein A9 (S100A9) in autistic phenotypes. We utilized the BTBR T + tf/J (BTBR) mouse, a reliable preclinical model for autism that displays core behavioral features of autism as well as persistent immune dysregulation. A combination of behavioral, pharmacological, immunological, genetic, molecular, and transcriptomics approaches were used to uncover the potential role of S100A9 in autism. Significant overexpression of microglial S100A9 was observed in the hippocampus of BTBR mice. BTBR mice displayed decreased social communication and increased repetitive behaviors compared to C57BL/6 mice. Interestingly, the above social dysfunction was attenuated by a pharmacological inhibitor of S100A9, accompanied by a significant reduction in the activated microglia morphological phenotype, inflammatory receptors, and proinflammatory cytokines. Notably, S100A9 inhibition decreased c-Fos+ cells and promoted myelination in the cornu ammonis 3 of BTBR mice. Furthermore, the promyelinating compound administration ameliorated the autism-relevant behaviors in BTBR mice. Our findings indicate that microglia-derived S100A9 triggers the neuroinflammation cascade, myelination deficits, and social dysfunction. Targeting S100A9 could, therefore, be a promising therapeutic strategy for neuroinflammation-related neurodevelopmental disorders.

Immune mechanisms of granuloma formation in sarcoidosis and tuberculosis

Sarcoidosis is a complex immune-mediated disease characterized by clusters of immune cells called granulomas. Despite major steps in understanding the cause of this disease, many questions remain. In this Review, we perform a mechanistic interrogation of the immune activities that contribute to granuloma formation in sarcoidosis and compare these processes with its closest mimic, tuberculosis, highlighting shared and divergent immune activities. We examine how Mycobacterium tuberculosis is sensed by the immune system; how the granuloma is initiated, formed, and perpetuated in tuberculosis compared with sarcoidosis; and the role of major innate and adaptive immune cells in shaping these processes. Finally, we draw these findings together around several recent high-resolution studies of the granuloma in situ that utilized the latest advances in single-cell technology combined with spatial methods to analyze plausible disease mechanisms. We conclude with an overall view of granuloma formation in sarcoidosis.

Exploiting innate immunity for cancer immunotherapy

Immunotherapies have revolutionized the treatment paradigms of various types of cancers. However, most of these immunomodulatory strategies focus on harnessing adaptive immunity, mainly by inhibiting immunosuppressive signaling with immune checkpoint blockade, or enhancing immunostimulatory signaling with bispecific T cell engager and chimeric antigen receptor (CAR)-T cell. Although these agents have already achieved great success, only a tiny percentage of patients could benefit from immunotherapies. Actually, immunotherapy efficacy is determined by multiple components in the tumor microenvironment beyond adaptive immunity. Cells from the innate arm of the immune system, such as macrophages, dendritic cells, myeloid-derived suppressor cells, neutrophils, natural killer cells, and unconventional T cells, also participate in cancer immune evasion and surveillance. Considering that the innate arm is the cornerstone of the antitumor immune response, utilizing innate immunity provides potential therapeutic options for cancer control. Up to now, strategies exploiting innate immunity, such as agonists of stimulator of interferon genes, CAR-macrophage or -natural killer cell therapies, metabolic regulators, and novel immune checkpoint blockade, have exhibited potent antitumor activities in preclinical and clinical studies. Here, we summarize the latest insights into the potential roles of innate cells in antitumor immunity and discuss the advances in innate arm-targeted therapeutic strategies.