Citations

Abstract Introduction The underlying immunopathogenesis of inflammatory arthritis (IA) immune-related adverse event (irAE) remains obscure. Unlike rheumatoid arthritis (RA), where autoantibodies and B cell dysfunction are central features, the contribution of humoral immunity to IA-irAE is unclear. Methods Here, we performed immunophenotyping of peripheral blood from IA-irAE patients, and compared them with seronegative RA patients, ICI-treated patients without irAE, and healthy controls. Results IA-irAE was marked with increased cytotoxic gene expression and metabolic activation in T cells, and reduced CXCR3 and CCR6 expression in CD4+ T cells. Contrary to seronegative RA, IA-irAE patients displayed no significant elevation in autoantibody levels or atypical CD11c+CD21⁻ B cells. IA-irAE was further characterized by elevated levels of IL-6, IL-12, and type I IFN, which correlated with the T cell activation phenotypes. Conclusion Altogether, our findings define IA-irAE as a disease with certain immunological features distinctive from RA, representing a potentially T cell driven, autoantibody-independent autoimmunity. These results offer insights into immune tolerance breakdown and therapeutic targeting in irAEs. Funding Source National Institute of Arthritis and Musculoskeletal and Skin Diseases Mark E. and Mary A. Davis Initiative in Rheumatoid Arthritis Research Mayo Foundation for Medical Education and Research Topic Categories Basic Autoimmunity (BA)

Objective We aim to identify risk factors to enable stratification of patients' susceptibility to inflammatory arthritis immune‐related adverse events (IA‐irAEs). This retrospective study mainly examines whether preexisting osteoarthritis (OA) increases the likelihood of de novo IA‐irAEs. Methods The prevalence of OA among immune checkpoint inhibitor (ICI)–treated patients who developed IA‐irAE, those who developed other types of irAEs but not IA (non‐IA irAEs), and those who did not develop any irAEs (non‐irAEs) were compared. Electronic medical records were reviewed to extract demographic, clinical, and laboratory data. Group comparisons and logistic regression analyses were performed. Results A total of 181 de novo IA‐irAE patients, 140 non‐IA irAE patients, and 170 non‐irAE patients were included. The prevalence of OA was significantly higher in the IA‐irAE group (69%) than in the non‐IA irAE group (48%) and the non‐irAE group (48%) (both P < 0.001). The IA‐irAE group demonstrated a higher frequency of multisite OA, with more predominant hand involvement (62%) than the non‐IA irAE with OA group (13%) and the non‐irAE with OA group (13%) (both P < 0.001). A family history of autoimmune disease (AID) (odds ratio [OR] 2.03, 95% confidence interval [CI] 1.02–4.05), preexisting OA (OR 2.88, 95% CI 1.85–4.52), and melanoma (OR 2.63, 95% CI 1.56–4.47) were identified as risk factors for the development of IA‐irAE. Conclusion OA was more prevalent among ICI‐treated patients developing IA‐irAE than those who were not. Hand OA was the most common OA pattern in IA‐irAE patients. Preexisting OA, melanoma, and a family history of AID were associated with IA‐irAE.

Abstract B cell activation and differentiation into antibody-secreting cells require extensive metabolic and epigenetic remodeling, yet the molecular mechanisms that integrate these programs remain incompletely understood. ATP-citrate lyase (ACLY) links glucose metabolism to acetyl-CoA production, supporting lipid biosynthesis and protein acetylation. However, its role in humoral immunity has not been fully defined. Here, using genetic and integrated multi-omics approaches, we show that B cell activation is accompanied by coordinated metabolic, transcriptional, and epigenetic reprograming. Although ACLY is dispensable for B cell development and homeostasis, it is required to establish chromatin accessibility programs in activated B cells, with a more pronounced impact on the epigenetic landscape than on transcriptional output. ACLY-deficient B cells exhibit profound defects in TLR and BCR elicited activation, survival and metabolic fitness ex vivo . In vivo , B cell-intrinsic loss of ACLY results in impaired antigen-specific antibody production, associated with reduced germinal center and plasmablast formation, but normal homeostatic proliferation. Deletion of ACLY after B cell activation reduces plasmablast generation in vivo , indicating a continued requirement for ACLY beyond the initial activation phase. Together, these findings identify ACLY as a central regulator that links metabolism to epigenetic programing that supports B cell activation and humoral immunity.

The underlying immunopathogenesis of inflammatory arthritis (IA) immune-related adverse event (irAE) remains obscure. Unlike rheumatoid arthritis (RA), where autoantibodies and B cell dysfunction are central features, the contribution of humoral immunity to IA-irAE is unclear. Here, we performed immunophenotyping of peripheral blood from patients with IA-irAE and compared them with patients with seronegative RA, immune checkpoint inhibition–treated patients without irAE, and healthy controls. IA-irAE was marked with increased cytotoxic gene expression and metabolic activation in T cells and reduced CXCR3 and CCR6 expression in CD4 + T cells. Contrary to seronegative RA, patients with IA-irAE displayed no substantial elevation in autoantibody levels or atypical CD11c + CD21 − B cells. IA-irAE was further characterized by elevated levels of interleukin-6 (IL-6), IL-12, and type I interferon, which correlated with the T cell activation phenotypes. Together, our findings define IA-irAE as a disease with certain immunological features distinctive from RA, representing a potentially T cell–driven, autoantibody-independent autoimmunity. These results offer insights into immune tolerance breakdown and therapeutic targeting in irAEs.

ABSTRACT Objective Identifying risk factors enables stratification of patients’ susceptibility to inflammatory arthritis immune-related adverse events (IA-irAE). This retrospective study examines whether preexisting osteoarthritis (OA) increases the likelihood of de novo IA in patients treated with immune checkpoint inhibitors (ICIs). Methods The prevalence of OA among ICI–treated patients who developed IA-irAE, those who developed other types of irAEs but not IA (non-IA irAE), and those who did not develop any irAEs (non-irAE) were compared. Electronic medical records were reviewed to extract demographic, clinical and laboratory data. Group comparisons and logistic regression analyses were performed. Results 181 de novo IA-irAE patients, 140 non-IA irAE patients and 170 non-irAE patients were included. The prevalence of OA was significantly higher in the IA-irAE group (69%) than the non-IA irAE group (48%) and the non-irAE group (48%) (both p < 0.001). The IA-irAE group demonstrated a higher frequency of multisite OA, with predominant hand involvement (62%) than the non-IA irAE with OA group (13%) and the non-irAE with OA group (13%) (both p < 0.001). A family history of autoimmune disease (AID) (OR 2.03, 95% CI 1.02–4.05), preexisting OA (OR 2.88, 95% CI 1.85–4.52) and melanoma (OR 2.63, 95% CI 1.56–4.47) were identified as risk factors for the development of IA-irAE. Conclusions OA was more prevalent among ICI-treated patients developing IA-irAE than those who did not. Hand OA was the most common OA pattern in IA-irAE patients. Preexisting OA, melanoma and a family history of AID were risk factors for IA-irAE.

Abstract Description During the humoral immune response, B cells undergo rapid metabolic reprogramming with a high demand for nutrients, which are vital to sustain the formation of the germinal centers (GCs). Rag-GTPases sense amino acid availability to modulate the mechanistic target of rapamycin complex 1 (mTORC1) pathway and suppress transcription factor EB (TFEB) and transcription factor enhancer 3 (TFE3). However, how Rag-GTPases coordinate amino acid sensing, mTORC1 activation, and TFEB/TFE3 activity in humoral immunity remains undefined. Here, we show that B cell-intrinsic Rag-GTPases are critical for the development and activation of B cells. RagA/RagB deficient B cells fail to form GCs, produce antibodies, and generate plasmablasts in both T-dependent (TD) and T-independent (TI) humoral immune responses. Deletion of RagA/RagB in GC B cells leads to abnormal dark zone (DZ) to light zone (LZ) ratio and reduced affinity maturation. Mechanistically, the Rag-GTPase complex constrains TFEB/TFE3 activity to prevent mitophagy dysregulation and maintain mitochondrial fitness in B cells, which are independent of canonical mTORC1 activation. TFEB/TFE3 deletion restores B cell development, GC formation in Peyer’s patches and TI humoral immunity, but not TD humoral immunity in the absence of Rag-GTPases. Collectively, our data establish Rag-GTPase-TFEB/TFE3 pathway as an mTORC1 independent mechanism to coordinating nutrient sensing and mitochondrial metabolism in B cells. Funding Sources National Institute of Allergy and Infectious Diseases (NIAID) - AI162678 National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) - AR077518 Topic Categories Immune Response Regulation: Molecular Mechanisms (IRM)

Abstract B cell activation is accompanied by dynamic metabolic reprogramming, supported by a multitude of nutrients that include glucose, amino acids, and fatty acids. Although several studies have indicated that fatty acid mitochondrial oxidation is critical for immune cell functions, contradictory findings have been reported. Carnitine palmitoyltransferase II (CPT2) is a critical enzyme for long-chain fatty acid oxidation in mitochondria. In this study, we test the requirement of CPT2 for humoral immunity using a mouse model with a lymphocyte-specific deletion of CPT2. Stable [13C] isotope tracing reveals highly reduced fatty acid–derived citrate production in CPT2-deficient B cells. Yet, CPT2 deficiency has no significant impact on B cell development, B cell activation, germinal center formation, and Ab production upon either thymus-dependent or -independent Ag challenges. Together, our findings indicate that CPT2-mediated fatty acid oxidation is dispensable for humoral immunity, highlighting the metabolic flexibility of lymphocytes.

Abstract Although the functions of tyrosine phosphatases in T‐cell biology have been extensively studied, our knowledge on the contribution of serine/threonine phosphatases in T cells remains poor. Protein phosphatase 2A (PP2A) is one of the most abundantly expressed serine/threonine phosphatases. It is important in thymocyte development and CD4 + T‐cell differentiation. Utilizing a genetic model in which its catalytic subunit alpha isoform (PP2A Cα) is deleted in T cells, we investigated its contribution to CD8 + T‐cell homeostasis and effector functions. Our results demonstrate that T‐cell intrinsic PP2A Cα is critically required for CD8 + T‐cell homeostasis in secondary lymphoid organs and intestinal mucosal site. Importantly, PP2A Cα–deficient CD8 + T cells exhibit reduced proliferation and survival. CD8 + T‐cell antibacterial response is strictly dependent on PP2A Cα. Expression of Bcl2 transgene rescues CD8 + T‐cell homeostasis in spleens, but not in intestinal mucosal site, nor does it restore defective antibacterial responses. Finally, proteomics and phosphoproteomics analyses reveal potential targets dependent on PP2A Cα, including mTORC1 and AKT. Thus, PP2A Cα is a key modulator of CD8 + T‐cell homeostasis and effector functions.

Abstract During the humoral immune response, B cells undergo rapid metabolic reprogramming with a high demand for nutrients, which are vital to sustain the formation of the germinal centers (GCs). Rag-GTPases sense amino acid availability to modulate the mechanistic target of rapamycin complex 1 (mTORC1) pathway and suppress transcription factor EB (TFEB) and transcription factor enhancer 3 (TFE3), members of the microphthalmia (MiT/TFE) family of HLH-leucine zipper transcription factors. However, how Rag-GTPases coordinate amino acid sensing, mTORC1 activation, and TFEB/TFE3 activity in humoral immunity remains undefined. Here, we show that B cell-intrinsic Rag-GTPases are critical for the development and activation of B cells. RagA/RagB deficient B cells fail to form GCs, produce antibodies, and generate plasmablasts in both T-dependent (TD) and T-independent (TI) humoral immune responses. Deletion of RagA/RagB in GC B cells leads to abnormal dark zone (DZ) to light zone (LZ) ratio and reduced affinity maturation. Mechanistically, the Rag-GTPase complex constrains TFEB/TFE3 activity to prevent mitophagy dysregulation and maintain mitochondrial fitness in B cells, which are independent of canonical mTORC1 activation. TFEB/TFE3 deletion restores B cell development, GC formation in Peyer’s patches and TI humoral immunity, but not TD humoral immunity in the absence of Rag-GTPases. Collectively, our data establish Rag-GTPase-TFEB/TFE3 axis as an mTORC1 independent mechanism to coordinating nutrient sensing and mitochondrial metabolism in B cells.

Abstract Seven different anti–PD-1 and PD-L1 mAbs are now widely used in the United States to treat a variety of cancer types, but no clinical trials have compared them directly. Furthermore, because many of these Abs do not cross-react between mouse and human proteins, no preclinical models exist in which to consider these types of questions. Thus, we produced humanized PD-1 and PD-L1 mice in which the extracellular domains of both mouse PD-1 and PD-L1 were replaced with the corresponding human sequences. Using this new model, we sought to compare the strength of the immune response generated by Food and Drug Administration–approved Abs. To do this, we performed an in vivo T cell priming assay in which anti–PD-1/L1 therapies were given at the time of T cell priming against surrogate tumor Ag (OVA), followed by subsequent B16-OVA tumor challenge. Surprisingly, both control and Ab-treated mice formed an equally robust OVA-specific T cell response at the time of priming. Despite this, anti–PD-1/L1-treated mice exhibited significantly better tumor rejection versus controls, with avelumab generating the best protection. To determine what could be mediating this, we identified the increased production of CX3CR1+PD-1+CD8+ cytotoxic T cells in the avelumab-treated mice, the same phenotype of effector T cells known to increase in clinical responders to PD-1/L1 therapy. Thus, our model permits the direct comparison of Food and Drug Administration–approved anti–PD-1/L1 mAbs and further correlates successful tumor rejection with the level of CX3CR1+PD-1+CD8 + T cells, making this model a critical tool for optimizing and better utilizing anti–PD-1/L1 therapeutics.