Rationale: TGF (transforming growth factor)-β is critically involved in myocardial injury, repair, and fibrosis, activating both Smad (small mothers against decapentaplegic)-dependent and non-Smad pathways. The in vivo role of TGF-β signaling in regulation of macrophage function is poorly understood. We hypothesized that in the infarcted myocardium, activation of TGF-β/Smad signaling in macrophages may regulate repair and remodeling. Objective: To investigate the role of macrophage-specific TGF-β Smad3 signaling in a mouse model of myocardial infarction and to dissect the mechanisms mediating Smad-dependent modulation of macrophage function. Methods and Results: TGF-βs markedly activated Smad3 in macrophages, without affecting Smad-independent pathways. Phagocytosis rapidly and directly activated macrophage Smad3, in the absence of active TGF-β release. MyS3KO (myeloid cell–specific Smad3 knockout) mice had no baseline defects but exhibited increased late mortality and accentuated dilative postmyocardial infarction remodeling. Adverse outcome in infarcted MyS3KO mice was associated with perturbations in phagocytic activity, defective transition of macrophages to an anti-inflammatory phenotype, scar expansion, and accentuated apoptosis of border zone cardiomyocytes. In vitro, Smad3 null macrophages exhibited reduced expression of genes associated with eat-me signals, such as Mfge8 (milk fat globule-epidermal growth factor factor 8), and reduced capacity to produce the anti-inflammatory mediators IL (interleukin)-10 and TGF-β1, and the angiogenic growth factor VEGF (vascular endothelial growth factor). Mfge8 partly rescued the phagocytic defect of Smad3 null macrophages, without affecting inflammatory activity. Impaired anti-inflammatory actions of Smad3 null macrophages were associated with marked attenuation of phagocytosis-induced PPAR (peroxisome proliferator-activated receptor) expression. MyS3KO mice had no significant alterations in microvascular density and interstitial fibrosis in remodeling myocardial segments. Conclusions: We demonstrate that Smad3 critically regulates function of infarct macrophages, by mediating acquisition of a phagocytic phenotype and by contributing to anti-inflammatory transition. Smad3-dependent actions in macrophages protect the infarcted heart from adverse remodeling.

Neuromuscular disorders are the most common neurological complication reported in PD-1 inhibitor-treated patients. Myasthenia gravis, immune-mediated myopathies, and Guillain-Barre syndrome are among commonly reported immune-related neuromuscular complications. HyperCKemia occurs frequently in patients with PD-1 inhibitor-associated myasthenia gravis, indicating coexisting myopathies or myocarditis. Oculobulbar weakness is a unique and common presentation of PD-1 inhibitor-associated immune-mediated myopathies with or without concomitant myasthenia gravis. High-dose steroid monotherapy may be associated with clinical deterioration in some patients with PD-1 inhibitor-associated myasthenia gravis, immune-mediated myopathies, or Guillain-Barre syndrome. PD-1 inhibitor-associated neuromuscular complications have some characteristic features compared to their idiopathic counterparts. Although steroid monotherapy is commonly used in non-neuromuscular autoimmune disorders triggered by anti-PD-1 therapy, this may lead to unfavorable outcomes in some patients with PD-1 inhibitor-associated neuromuscular complications.

Little is known about the regulatory roles of specific soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins in cytotoxic lymphocytes. Recent information suggests that mutations in the SNARE protein syntaxin 11 result in a form of familial hemophagocytic lymphohistiocytosis (FHL). Because genetic abnormalities in key granule components (e.g., perforin) or in regulators of secretion (e.g., Munc13–4) underlie the other identified forms of FHL, we assessed whether syntaxin 11 might also serve a related regulatory role. We determined that syntaxin 11 is expressed in NK cells and activated CTLs and is located in discrete membrane-associated structures in the cytoplasm. Enhanced expression of syntaxin 11 augments the secretion and killing of tumor targets, and suppression of syntaxin 11 expression inhibits these functions. Our data identify and characterize a role for syntaxin 11 in granule exocytosis and in the generation of cell-mediated killing. These results also provide new insights on the mechanisms of hemopoietic dysregulation in FHL.

Summary Background Antibody-dependent pathogenicity is suggested in multiple sclerosis (MS) by intrathecal immunoglobulin production, IgG and complement deposition in the most common immunopathological lesion subtype (pattern II), and by a recent report that 47% of MS patients’ sera contain a glial potassium-channel-specific-IgG(inwardly-rectifying, Kir4.1). Our study’s aims were to determine, in MS serum and CSF, the frequency and specificity of Kir4.1-binding-IgG and, in demyelinating MS lesions, whether Kir4.1-immunoreactivity is retained or lost. Methods We tested by ELISA(Kir4.1-peptide 83–120) sera from 286 clinically and geographically diverse MS patients (229 population-based and 57 clinic-based),99 healthy controls and 109 disease controls, and cerebrospinal fluid [CSF] from 25 MS and 22 controls. CSFs and clinic-based MS-subset serum (50)were tested on functional Kir4.1-expressing cells, using methodologies validated for detecting clinically-pertinent neural plasma membrane-reactive autoantibodies: immunofluorescence and immunoprecipitation (solubilized recombinant human Kir4.1). We evaluated Kir4.1-immunoreactivity in brain from 15 archival histopathologically-confirmed MS cases(22 plaques: 8 early active, 8 inactive, 6 remyelinated; 13 periplaque regions)and compared 3 non-neurological cases (8 normal-appearing white/gray matter regions). Findings Kir4.1-peptide-ELISA reactivity was rare and did not differ significantly for 286 MS or 208 control sera (both 1%); no CSF was positive. IgGin 0/50 clinic-based MS sera immunoprecipitated Kir4.1, but control Kir4.1-specific-IgG did. By immunofluorescence,1/50 MS sera yielded faint plasmalemmal staining on both Kir4.1-expressing and non-expressing cells; 16/50 bound faintly to intracellular components. In all cases, IgG binding was quenched by absorption with liver powder or non-transfected cell lysates. Control Kir4.1-specific-IgG binding was quenched only by Kir4.1 protein-containing lysates. IgG in 0/25 MS CSFs bound to Kir4.1-transfected cells, live or fixed. Glial Kir4.1-immunoreactivity was increased relative to baseline normal brain expression (3 controls) in early active and remyelinated MS lesions, and in periplaque white matter (15 patients). Interpretation We did not find Kir4.1-specific-IgG in MS sera or CSF, nor Kir4.1 loss from glial cells in active demyelinating MS lesions. Serological testing for Kir4.1-IgG is unlikely to aid MS diagnosis. The target antigen of MS remains elusive. Funding The National Institutes of Health, the National Multiple Sclerosis Society and the Mayo Clinic Robert and Arlene Kogod Center on Aging.