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Proteinase-activated receptor-2 (PAR2), which modulates inflammatory responses, is elevated in the central nervous system in multiple sclerosis (MS) and in its murine model, experimental autoimmune encephalomyelitis (EAE). In PAR2-null mice, disease severity of EAE is markedly diminished. We therefore tested whether inhibiting PAR2 activation in vivo might be a viable strategy for the treatment of MS. Using the EAE model, we show that a PAR2 antagonist, the pepducin palmitoyl-RSSAMDENSEKKRKSAIK-amide (P2pal-18S), attenuates EAE progression by affecting immune cell function. P2pal-18S treatment markedly diminishes disease severity and reduces demyelination, as well as the infiltration of T-cells and macrophages into the central nervous system. Moreover, P2pal-18S decreases granulocyte-macrophage colony-stimulating factor (GM-CSF) production and T-cell activation in cultured splenocytes and prevents macrophage polarization in vitro. We conclude that PAR2 plays a key role in regulating neuroinflammation in EAE and that PAR2 antagonists represent promising therapeutic agents for treating MS and other neuroinflammatory diseases. SIGNIFICANCE STATEMENT: Proteinase-activated receptor-2 modulates inflammatory responses and is increased in multiple sclerosis lesions. We show that the proteinase-activated receptor-2 antagonist palmitoyl-RSSAMDENSEKKRKSAIK-amide reduces disease in the murine experimental autoimmune encephalomyelitis model of multiple sclerosis by inhibiting T-cell and macrophage activation and infiltration into the central nervous system, making it a potential treatment for multiple sclerosis.
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Encefalomielite Autoimune Experimental , Esclerose Múltipla , Camundongos , Animais , Encefalomielite Autoimune Experimental/tratamento farmacológico , Encefalomielite Autoimune Experimental/patologia , Doenças Neuroinflamatórias , Receptor PAR-2 , Esclerose Múltipla/tratamento farmacológico , Camundongos Knockout , Amidas/uso terapêutico , Camundongos Endogâmicos C57BLRESUMO
BACKGROUND: Risk stratification tools for patients with advanced melanoma (AM) treated with immune checkpoint inhibitors (ICI) are lacking. We identified a new prognostic model associated with overall survival (OS). PATIENTS AND METHODS: A total of 318 treatment naïve patients with AM receiving ICI were collected from a multi-centre retrospective cohort study. LASSO Cox regression identified independent prognostic factors associated with OS. Model validation was carried out on 500 iterations of bootstrapped samples. Harrel's C-index was calculated and internally validated to outline the model's discriminatory performance. External validation was carried out in 142 advanced melanoma patients receiving ICI in later lines. RESULTS: High white blood cell count (WBC), high lactate dehydrogenase (LDH), low albumin, Eastern Cooperative Oncology Group (ECOG) performance status ≥1, and the presence of liver metastases were included in the model. Patients were parsed into 3 risk groups: favorable (0-1 factors) OS of 52.9 months, intermediate (2-3 factors) OS 13.0 months, and poor (≥4 factors) OS 2.7 months. The C-index of the model from the discovery cohort was 0.69. External validation in later-lines (N = 142) of therapy demonstrated a c-index of 0.65. CONCLUSIONS: Liver metastases, low albumin, high LDH, high WBC, and ECOG≥1 can be combined into a prognostic model for AM patients treated with ICI.
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Neoplasias Hepáticas , Melanoma , Humanos , Prognóstico , Inibidores de Checkpoint Imunológico/farmacologia , Inibidores de Checkpoint Imunológico/uso terapêutico , Estudos Retrospectivos , Melanoma/patologia , AlbuminasRESUMO
Importance: Immune-related adverse events (irAEs) due to immune checkpoint blockade (ICB) have been shown to be positively associated with survival. Among patients with metastatic melanoma, evidence supporting this association has been conflicting, while ipilimumab-nivolumab combination ICB has been examined only in small clinical cohorts. Objective: To examine the association between irAEs and survival among patients with metastatic melanoma, in particular for those receiving combination ICB. Design, Setting, and Participants: A retrospective cohort of 492 consecutive patients with metastatic melanoma treated with ICB at 2 tertiary and 4 regional cancer centers in Alberta, Canada, from August 1, 2013, to May 31, 2020, was observed. Patients were aged 18 years or older with metastatic melanoma agnostic to primary site, who received 1 or more doses of an anti-programmed cell death protein 1 agent as single or combination ICB. Clinically significant irAEs requiring systemic corticosteroids and/or treatment delay were captured. To minimize immortal time bias, only patients surviving 12 weeks after ICB initiation were included in survival analyses. Statistical analysis was conducted on December 10, 2021. Exposures: Development of irAEs requiring systemic corticosteroids and/or treatment delay. Main Outcomes and Measures: The primary outcome was overall survival (OS), with the association of irAE development with OS assessed via Kaplan-Meier and Cox proportional hazards regression analyses. The association of hospitalization for irAEs and ICB resumption after irAE with OS was examined. Results: Among 492 patients, the median age of those with irAEs was 61.8 years (IQR, 52.9-72.1 years), and the median age of those without irAEs was 65.5 years (IQR, 56.5-76.9 years), while sex distribution was comparable (137 of 198 men [69.2%] with irAEs vs 183 of 294 men [62.2%] without irAEs). There was an association between irAEs and OS both in the overall cohort (with irAEs: median OS, 56.3 months [95% CI, 38.2 months to not evaluable] vs without irAEs: median OS, 18.5 months [95% CI, 14.4-23.2 months]; P < .001) and in the 124 patients (25.2%) receiving combination ICB (with irAEs: median OS, 56.2 months [95% CI, 52.2 months to not evaluable] vs without irAEs: median OS, 19.0 months [95% CI, 6.6 months to not evaluable]; P < .001). Hospitalization for irAE did not alter this positive association with OS compared with outpatient treatment (median OS, not evaluable [95% CI, 31.5 months to not evaluable] vs median OS, 52.2 months [95% CI, 35.2 months to not evaluable]; P = .53), while resumption of ICB was associated with longer OS than not resuming ICB (median, 56.3 months [95% CI, 40.8 months to not evaluable] vs 31.5 months [95% CI, 21.0 months to not evaluable]; P = .009). A favorable independent association of irAEs with OS was confirmed in multivariable analysis (hazard ratio for death, 0.382 [95% CI, 0.254-0.576]; P < .001). Conclusions and Relevance: This study suggests an association between irAEs and OS for patients with metastatic melanoma, including those treated with combination ICB and those with severe irAEs requiring hospitalization. The potential benefit associated with ICB resumption after irAEs warrants further investigation.
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Melanoma , Humanos , Pessoa de Meia-Idade , Idoso , Estudos Retrospectivos , Distribuição por Sexo , Alberta , Melanoma/tratamento farmacológicoRESUMO
Recognition of pathogen-or-damage-associated molecular patterns is critical to inflammation. However, most pathogen-or-damage-associated molecular patterns exist within intact microbes/cells and are typically part of non-diffusible, stable macromolecules that are not optimally immunostimulatory or available for immune detection. Partial digestion of microbes/cells following phagocytosis potentially generates new diffusible pathogen-or-damage-associated molecular patterns, however, our current understanding of phagosomal biology would have these molecules sequestered and destroyed within phagolysosomes. Here, we show the controlled release of partially-digested, soluble material from phagolysosomes of macrophages through transient, iterative fusion-fission events between mature phagolysosomes and the plasma membrane, a process we term eructophagy. Eructophagy is most active in proinflammatory macrophages and further induced by toll like receptor engagement. Eructophagy is mediated by genes encoding proteins required for autophagy and can activate vicinal cells by release of phagolysosomally-processed, partially-digested pathogen associated molecular patterns. We propose that eructophagy allows macrophages to amplify local inflammation through the processing and dissemination of pathogen-or-damage-associated molecular patterns.
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Moléculas com Motivos Associados a Patógenos , Fagossomos , Alarminas/metabolismo , Humanos , Inflamação/metabolismo , Macrófagos , Moléculas com Motivos Associados a Patógenos/metabolismo , Fagocitose , Fagossomos/metabolismoRESUMO
BACKGROUND: Immuno-oncology (IO)-based therapies have been approved based on randomised clinical trials, yet a significant proportion of real-world patients are not represented in these trials. We sought to compare the outcomes of trial-ineligible vs. -eligible patients with advanced solid tumours treated with first-line (1L) IO therapy. PATIENTS AND METHODS: Using the International Metastatic Renal Cell Carcinoma (RCC) Database Consortium and the Alberta Immunotherapy Database, patients with advanced RCC, non-small-cell lung cancer (NSCLC) or melanoma treated with 1L PD-(L)1 inhibition-based therapy were included. Trial eligibility was retrospectively determined as per commonly used exclusion criteria. The outcomes of interest were overall survival (OS), overall response rate (ORR), treatment duration (TD) and time to next treatment (TTNT). RESULTS: A total of 395 of 1241 (32%) patients were deemed trial-ineligible. The main reasons for ineligibility based on preselected exclusion criteria were Karnofsky performance status <70%/Eastern Cooperative Oncology Group performance status >1 (40%, 158 of 395), brain metastases (32%, 126 of 395), haemoglobin < 9 g/dL (16%, 63 of 395) and estimated glomerular filtration rate <40 mL/min (15%, 61 of 395). Between the ineligible vs. eligible groups, the median OS, ORR, median TD and median TTNT were 10.2 vs. 39.7 months (p < 0.01), 36% vs. 47% (p < 0.01), 2.7 vs. 6.9 months (p < 0.01) and 6.0 vs. 16.8 months (p < 0.01), respectively. Subgroup analyses showed statistically significant inferior OS, TD and TTNT for trial-ineligible vs. -eligible patients across all tumour types. Adjusted hazard ratios for death in RCC, NSCLC and melanoma were 1.84 (95% confidence interval [CI] 1.22-2.77), 2.21 (95% CI 1.58-3.11) and 1.82 (95% CI 1.21-2.74), respectively.. CONCLUSIONS: Thirty-two percent of real-world patients treated with contemporary 1L IO-based therapies were ineligible for clinical trials. Although one-third of the trial-ineligible patients responded to treatment, the overall trial-ineligible population had inferior outcomes than trial-eligible patients. These data may guide patient counselling and temper expectations of benefit.
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Ensaios Clínicos como Assunto , Inibidores de Checkpoint Imunológico/uso terapêutico , Neoplasias/tratamento farmacológico , Seleção de Pacientes , Idoso , Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Carcinoma Pulmonar de Células não Pequenas/imunologia , Carcinoma Pulmonar de Células não Pequenas/patologia , Carcinoma de Células Renais/tratamento farmacológico , Carcinoma de Células Renais/imunologia , Carcinoma de Células Renais/patologia , Bases de Dados Factuais , Definição da Elegibilidade , Feminino , Humanos , Inibidores de Checkpoint Imunológico/efeitos adversos , Neoplasias Renais/tratamento farmacológico , Neoplasias Renais/imunologia , Neoplasias Renais/patologia , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/imunologia , Neoplasias Pulmonares/patologia , Masculino , Melanoma/tratamento farmacológico , Melanoma/imunologia , Melanoma/patologia , Pessoa de Meia-Idade , Neoplasias/imunologia , Neoplasias/mortalidade , Neoplasias/patologia , Estudos Retrospectivos , Neoplasias Cutâneas/tratamento farmacológico , Neoplasias Cutâneas/imunologia , Neoplasias Cutâneas/patologia , Fatores de Tempo , Resultado do TratamentoRESUMO
The extracellular bone resorbing lacuna of the osteoclast shares many characteristics with the degradative lysosome of antigen-presenting cells. γ-Interferon-inducible lysosomal thiol reductase (GILT) enhances antigen processing within lysosomes through direct reduction of antigen disulfides and maintenance of cysteine protease activity. In this study, we found the osteoclastogenic cytokine RANKL drove expression of GILT in osteoclast precursors in a STAT1-dependent manner, resulting in high levels of GILT in mature osteoclasts, which could be further augmented by γ-interferon. GILT colocalized with the collagen-degrading cysteine protease, cathepsin K, suggesting a role for GILT inside the osteoclastic resorption lacuna. GILT-deficient osteoclasts had reduced bone-resorbing capacity, resulting in impaired bone turnover and an osteopetrotic phenotype in GILT-deficient mice. We demonstrated that GILT could directly reduce the noncollagenous bone matrix protein SPARC, and additionally, enhance collagen degradation by cathepsin K. Together, this work describes a previously unidentified, non-immunological role for GILT in osteoclast-mediated bone resorption.
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BACKGROUND: Metastatic uveal melanoma (MUM) is associated with poor survival and inferior response to immune checkpoint inhibitor (ICI) therapy when compared with metastatic cutaneous melanoma. Currently, prognostic biomarkers are lacking to guide treatment decisions. PATIENTS AND METHODS: We conducted a multicenter, retrospective cohort study using a centralized, province-wide cancer database in Alberta, Canada. We identified 37 patients with histologically confirmed MUM who received at least one dose of single-agent pembrolizumab or nivolumab, or combination therapy nivolumab and ipilimumab. A modified immune prognostic index (IPI), based on the previously reported lung immune prognostic index, was used to stratify patients into favorable and poor IPI groups. Survival analyses were conducted using the Kaplan-Meier method and Cox proportional hazards models, adjusting for baseline age (≥60) and ECOG performance status, to assess the associations between IPI and overall survival (OS). Time to treatment failure (TTF) was also assessed using the Kaplan-Meier method. The association between IPI and objective response rate was examined using chi-squared tests. Logistic regression was used to determine the association between IPI and immune-related adverse events (irAEs). RESULTS: Median OS was 15.6 (range 0.6-57.6) months with 45.9% 1-year survival rate at a median follow-up of 11.8 months. We found that a favorable IPI was significantly associated with OS [median 30.5 (12.0-not reached) months in the favorable IPI group compared with 4.6 (2.1-16.0) months in the poor IPI group (p = 0.001)] (HR=4.81, 95% CI; 1.64-14.10, p = 0.004), TTF [median 5.1 (95% CI; 2.1-10.4) months in the favorable IPI group compared with 3.7 (95% CI; 1.4-6.4) months in the poor IPI group (p = 0.0191)], and irAE (HR=6.67, 95% CI; 1.32-33.69, p = 0.0220). CONCLUSIONS: The modified IPI may be a useful tool in clinical practice for identifying MUM patients who are more likely to experience irAEs and realize a survival benefit from ICI treatment.
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Inibidores de Checkpoint Imunológico/uso terapêutico , Melanoma/tratamento farmacológico , Melanoma/imunologia , Neoplasias Uveais/tratamento farmacológico , Neoplasias Uveais/imunologia , Idoso , Feminino , Humanos , Estimativa de Kaplan-Meier , L-Lactato Desidrogenase/sangue , Contagem de Linfócitos , Masculino , Melanoma/mortalidade , Pessoa de Meia-Idade , Neutrófilos , Prognóstico , Estudos Retrospectivos , Resultado do Tratamento , Neoplasias Uveais/mortalidadeRESUMO
On November 8th, 2019, the Cumming School of Medicine at the University of Calgary hosted the 11th annual Leaders in Medicine (LIM) Research Symposium. Dr. Donald A. Redelmeier, Professor at the University of Toronto and Canada Research Chair in Medical Decision Sciences, served as the keynote speaker with a talk entitled "Pitfalls of Reasoning and Clinical Medicine". In addition, there were five oral and 64 poster presentations. These presentations covered topics ranging from health promotion to neuroimaging. The event celebrated the continuing success and diversity of the LIM program and the training of clinician-scientists at the University of Calgary.
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INTRODUCTION: Vascular comorbidities are prevalent among people with multiple sclerosis (MS) and have adverse disease-related consequences. In the general population, physical activity (PA) and exercise training have proven beneficial at all levels of vascular disease risk management. People with MS exhibit particularly low rates of PA; therefore, PA represents a modifiable health behavior for potentially managing vascular comorbidity risk in MS, and in turn, reducing disease burden. However, points of evidence justifying such an approach have yet to be summarized. OBJECTIVE: To conduct a scoping review of existing evidence linking PA and exercise training to potential modification of vascular comorbidities and related risk factors in people with MS. METHODS: We searched five electronic databases (PubMed, Ovid MEDLINE, Embase, PsycINFO, and CINAHL Plus) from inception to November 2017, for articles involving relevant vascular comorbidities (obesity, hyperlipidemia, heart disease, hypertension, and diabetes) in people with MS in conjunction with measures of PA, physical fitness, sedentary behavior, or exercise training. Studies were limited to English-language and primary research articles. Data were extracted and summarized by comorbidity type and study design (observational vs. interventional). RESULTS: Our initial search identified 1028 articles; subsequent screening resulted in 34 articles meeting the final inclusion criteria, including both observational (nâ¯=â¯17) and interventional (nâ¯=â¯17) studies. Most of the articles reported on obesity (nâ¯=â¯29), although evidence surrounding hyperlipidemia (nâ¯=â¯5), arterial function and hypertension (nâ¯=â¯5), and diabetes (nâ¯=â¯5) was also identified. Data supporting a beneficial role for PA or exercise training could be drawn from each comorbidity category. Overall, 14 of the 17 observational studies identified (82.4%) reported an association between higher levels of PA or cardiorespiratory fitness, or decreased sedentary behavior, and better function of at least one risk factor related to vascular comorbid conditions in people with MS. The efficacy of exercise training in limiting vascular comorbidity risk and burden was dependent upon intervention type and duration, with 9 of 17 interventional studies (52.9%) reporting improvement in at least one relevant measure of vascular comorbidity in participants with MS. CONCLUSIONS: Evidence points to a potential relationship between PA and exercise and risk factors related to vascular comorbidities in people with MS. PA and exercise training interventions may represent an effective therapeutic strategy for managing vascular comorbidities in people with MS, justifying further investigation.
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Comorbidade , Terapia por Exercício , Exercício Físico , Esclerose Múltipla/reabilitação , Doenças Vasculares/reabilitação , Terapia por Exercício/estatística & dados numéricos , Humanos , Esclerose Múltipla/epidemiologia , Doenças Vasculares/epidemiologiaRESUMO
In addition to debris clearance and antimicrobial function, versatile organelles known as phagosomes play an essential role in the processing of exogenous antigen in antigen presenting cells. While there has been much attention on human leukocyte antigen haplotypes in the determination of antigenic peptide repertoires, the lumenal biochemistries within phagosomes and endosomes are emerging as equally-important determinants of peptide epitope composition and immunodominance. Recently, the lumenal redox microenvironment within these degradative compartments has been shown to impact two key antigenic processing chemistries: proteolysis by lysosomal cysteine proteases and disulfide reduction of protein antigens. Through manipulation of the balance between oxidative and reductive capacities in the phagosome-principally by modulating NADPH oxidase (NOX2) and γ-interferon-inducible lysosomal thiol reductase (GILT) activities-studies have demonstrated changes to antigen processing patterns leading to modified repertoires of antigenic peptides available for presentation, and subsequently, altered disease progression in T cell-driven autoimmunity. This review focuses on the mechanisms and consequences of redox-mediated phagosomal antigen processing, and the potential downstream implications to tolerance and autoimmunity.
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Apresentação de Antígeno/imunologia , Doenças Autoimunes/imunologia , Inflamação/imunologia , NADPH Oxidases/metabolismo , Fagossomos/imunologia , Animais , Doenças Autoimunes/patologia , Humanos , Inflamação/patologia , Oxirredução , Transdução de SinaisRESUMO
The synthetic supercooling drug, icilin, and its primary receptor target, the cation channel transient receptor potential (TRP) melastatin-8 (TRPM8), have been described as potent negative regulators of inflammation in the colon. The aim of this study was to determine whether the anti-inflammatory action of icilin could potentially be used to treat autoimmune neuroinflammatory disorders, such as multiple sclerosis (MS). During experimental autoimmune encephalomyelitis (EAE)-a CD4+ T cell-driven murine model of MS-we found that both wild-type (WT) and TRPM8-deficient EAE mice were protected from disease progression during icilin treatment, as evidenced by delays in clinical onset and reductions in neuroinflammation. In vitro, icilin potently inhibited the proliferation of murine and human CD4+ T cells, with the peripheral expansion of autoantigen-restricted T cells similarly diminished by the administration of icilin in mice. Attenuation of both TRPM8-/- and TRP ankyrin-1-/- T-cell proliferation by icilin was consistent with the WT phenotype, which suggests a mechanism that is independent of these channels. In addition, icilin treatment altered the expressional profile of activated CD4+ T cells to one that was indicative of restricted effector function and limited neuroinflammatory potential. These findings identify a potent anti-inflammatory role for icilin in lymphocyte-mediated neuroinflammation and highlight clear pleiotropic effects of the compound beyond classic TRP channel activation.-Ewanchuk, B. W., Allan, E. R. O., Warren, A. L., Ramachandran, R., Yates, R. M. The cooling compound icilin attenuates autoimmune neuroinflammation through modulation of the T-cell response.
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Cálcio/metabolismo , Encefalomielite Autoimune Experimental/prevenção & controle , Inflamação/prevenção & controle , Pirimidinonas/farmacologia , Linfócitos T/imunologia , Canal de Cátion TRPA1/fisiologia , Canais de Cátion TRPM/fisiologia , Animais , Agonistas dos Canais de Cálcio/farmacologia , Células Cultivadas , Encefalomielite Autoimune Experimental/imunologia , Encefalomielite Autoimune Experimental/patologia , Feminino , Inflamação/imunologia , Inflamação/patologia , Mediadores da Inflamação/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Linfócitos T/efeitos dos fármacosRESUMO
BACKGROUND: Hypomethylation of the cathepsin Z locus has been proposed as an epigenetic risk factor for multiple sclerosis (MS). Cathepsin Z is a unique lysosomal cysteine cathepsin expressed primarily by antigen presenting cells. While cathepsin Z expression has been associated with neuroinflammatory disorders, a role for cathepsin Z in mediating neuroinflammation has not been previously established. METHODS: Experimental autoimmune encephalomyelitis (EAE) was induced in both wildtype mice and mice deficient in cathepsin Z. The effects of cathepsin Z-deficiency on the processing and presentation of the autoantigen myelin oligodendrocyte glycoprotein, and on the production of IL-1ß and IL-18 were determined in vitro from cells derived from wildtype and cathepsin Z-deficient mice. The effects of cathepsin Z-deficiency on CD4+ T cell activation, migration, and infiltration to the CNS were determined in vivo. Statistical analyses of parametric data were performed by one-way ANOVA followed by Tukey post-hoc tests, or by an unpaired Student's t test. EAE clinical scoring was analyzed using the Mann-Whitney U test. RESULTS: We showed that mice deficient in cathepsin Z have reduced neuroinflammation and dramatically lowered circulating levels of IL-1ß during EAE. Deficiency in cathepsin Z did not impact either the processing or the presentation of MOG, or MOG- specific CD4+ T cell activation and trafficking. Consistently, we found that cathepsin Z-deficiency reduced the efficiency of antigen presenting cells to secrete IL-1ß, which in turn reduced the ability of mice to generate Th17 responses-critical steps in the pathogenesis of EAE and MS. CONCLUSION: Together, these data support a novel role for cathepsin Z in the propagation of IL-1ß-driven neuroinflammation.
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Catepsina Z/metabolismo , Encefalomielite Autoimune Experimental/complicações , Epilepsia/etiologia , Animais , Células Apresentadoras de Antígenos/metabolismo , Células Apresentadoras de Antígenos/patologia , Antígenos CD/metabolismo , Linfócitos T CD4-Positivos/efeitos dos fármacos , Linfócitos T CD4-Positivos/patologia , Catepsina Z/genética , Quimiocina CXCL9/farmacologia , Modelos Animais de Doenças , Encefalomielite Autoimune Experimental/induzido quimicamente , Encefalomielite Autoimune Experimental/genética , Encefalomielite Autoimune Experimental/cirurgia , Interleucina-18/genética , Interleucina-18/metabolismo , Interleucina-1beta/genética , Interleucina-1beta/metabolismo , Leucócitos/patologia , Macrófagos/efeitos dos fármacos , Macrófagos/metabolismo , Macrófagos/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Glicoproteína Mielina-Oligodendrócito/metabolismo , Glicoproteína Mielina-Oligodendrócito/toxicidade , Fragmentos de Peptídeos/toxicidade , Fagossomos/metabolismo , Medula Espinal/patologiaRESUMO
Proteolysis and the reduction of disulfides, both major components of protein degradation, are profoundly influenced by phagosomal redox conditions in macrophages. We evaluated the activation of phagocytic receptors that are known to influence activation of the phagocyte NADPH oxidase (NOX2), and its effect on phagosomal protein degradation. Population-based and single phagosome analyses of phagosomal chemistries in murine macrophages revealed that activation of NOX2 via the Fcγ receptor (FcγR) during phagocytosis decreased rates of proteolysis and disulfide reduction. Immunoglobulin G (IgG)-stimulated reactive oxygen species (ROS) production and the inhibition of phagosomal proteolysis and disulfide reduction were dependent on NOX2, FcγR and protein kinase C (PKC)/spleen tyrosine kinase (Syk) signaling. In contrast, low levels of ROS production were observed following the phagocytosis of unopsonized beads, which resulted in higher rates of phagosomal proteolysis and disulfide reduction. Phagosomes displayed autonomy with respect to FcγR-mediated differences in NOX2 activation and proteolysis, as phagosomes containing unopsonized cargo retained low NOX2 activation and high proteolysis even in the presence of phagosomes containing IgG-opsonized cargo in the same macrophage. These results show that opsonization of phagocytic cargo results in vastly different phagosomal processing of proteins through the FcγR-triggered, PKC/Syk-dependent local assembly and activation of NOX2.