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Background: Insight into the pathomechanism of atopic diseases demonstrated a pivotal role of the cytokines interleukin‐4 (IL‐4) and IL‐13, which has spurred the development of tailored therapeutics targeting their common IL‐4 receptor (IL‐4R). However, several aspects of the IL‐4R system remain ill‐defined in humans. Methods: We used multicolor spectral flow cytometry to characterize IL‐4R subunit expression in 28 human immune cell subsets on protein and mRNA levels and assessed their subcellular distribution by applying a specifically adapted protocol that avoided influence of fixation and permeabilization on fluorochrome and antibody performance. In patients, we investigated possible changes in IL‐4Rα distribution before and during treatment with dupilumab, a monoclonal antibody‐targeting IL‐4Rα. Results: Whereas all immune cell subsets investigated expressed IL‐4Rα and common γ chain protein and mRNA, expression of IL‐13Rα1 was restricted to myeloid and B cells. Interestingly, some cells contained considerably more intracellular IL‐4R protein than on their surface. Naive B cells were found to carry the highest levels of IL‐4Rα distributed evenly between surface and intracellular space, whereas IL‐4Rα was found predominantly in intracellular pools in neutrophils. In patients with atopic diseases treated with dupilumab, we observed that engagement of IL‐4Rα by dupilumab resulted in internalization of the antibody and decreased total IL‐4Rα expression. Notably, even after months of treatment not all intracellular IL‐4Rα molecules were occupied by dupilumab, indicating the presence of a "dormant" intracellular IL‐4Rα pool that could be mobilized upon certain extrinsic or intrinsic cues. Conclusion: Collectively, our findings suggest that distinct human immune cell subsets contain surface and intracellular IL‐4R pools, which are differently affected by targeted biologic treatment. [ABSTRACT FROM AUTHOR]

Background: Systemic sclerosis (SSc) is a multiorgan autoimmune disease characterized by inflammation, vascular modification, and progressive fibrosis of the skin and several visceral organs. Innate and adaptive immune cells, including myeloid, B and T cells, are believed to be central to the pathogenesis of SSc. However, the role and functional state of neutrophil granulocytes (neutrophils) are ill‐defined in SSc. Methods: We performed a prospective study of neutrophils freshly isolated from SSc patients and healthy donors (HD) by measuring in these neutrophils (i) functional cell surface markers, including CD16, CD62L, CD66b, CD66c, CXCR1, CXCR2, and CXCR4; (ii) cytokine‐activated intracellular signal transducer and activator of transcription (STAT) pathways, such as phosphorylated STAT3 (pSTAT3), pSTAT5, and pSTAT6; (iii) production of neutrophil extracellular traps (NET) and intracellular myeloperoxidase (MPO); and (iv) phagocytosis of bacteria by the neutrophils. Results: Neutrophils of SSc patients expressed lower CD16 and CD62L and higher pSTAT3 and pSTAT6 compared to HD. Moreover, neutrophils of SSc patients lacked CXCR1 and CXCR2, the receptors responding to the potent neutrophil chemoattractant CXCL8. Neutrophils of SSc patients were also deficient in MPO levels, NET formation, and phagocytosis of bacteria. Conclusions: Neutrophils of patients with SSc display several functional defects affecting cell migration, NET formation, and phagocytosis of bacteria. [ABSTRACT FROM AUTHOR]

Background: Biologic agents (also termed biologics or biologicals) are becoming increasingly important in the treatment of immune‐mediated diseases. However, the diversity of clinical trials along with the fast pace of publication makes it difficult to determine the level of evidence for the use of a biologic for a given disorder. To address this challenge, we are publishing a series of systematic reviews evaluating the safety and efficacy of B cell–targeting biologics for the treatment of immune‐mediated diseases. In this article, we have assessed the safety and efficacy of belimumab, a fully human IgG1 monoclonal antibody targeting the cytokine B cell–activating factor (BAFF). Objective: To evaluate belimumab's safety and efficacy for the treatment of immune‐mediated disorders compared to placebo, conventional treatment or other biologics. Methods: The Preferred Reporting Items for Systematic reviews and Meta‐Analyses (PRISMA) checklist guided the reporting of the data. We searched the PubMed database between October 4, 2016, and June 23, 2019, concentrating on immune‐mediated disorders. Results: The literature search identified 583 articles. After screening titles and abstracts against the inclusion and exclusion criteria and assessing full texts, 17 articles were finally included in a narrative synthesis. Conclusions: Belimumab is both safe and effective for the treatment of systemic lupus erythematosus. Results were further promising for the use of belimumab in patients with rheumatoid arthritis and Sjögren's syndrome. Conversely, results using belimumab in patients with anti‐neutrophil cytoplasmic antibody (ANCA)‐associated vasculitis and myasthenia gravis were rather disappointing. [ABSTRACT FROM AUTHOR]