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Background and purpose: It is not known whether the route of administration affects the mechanisms of action of therapeutic immunoglobulin in chronic inflammatory demyelinating polyneuropathy (CIDP). The aim of this study, therefore, was to compare the immunomodulatory effects of intravenous (IVIg) and subcutaneous immunoglobulin (SCIg) in patients with CIDP and in IVIg‐treated common variable immunodeficiency (CVID) patients. Methods: Serum and peripheral blood mononuclear cell samples were obtained from 30 CIDP patients receiving IVIg, 10 CIDP patients receiving SCIg, and 15 patients with CVID receiving IVIg. Samples and clinical data were obtained prior to IVIg/SCIg and at 3 days, 7 days, and, in CIDP patients receiving IVIg, 21 days post‐administration. Serum cytokines were assessed by Luminex‐based multiplex assay and enzyme‐linked immunosorbent assay. Immune cells were characterized by flow cytometry. Results: Immune cell profiles of CIDP and CVID patients differed in frequencies of myeloid dendritic cells and cytotoxic natural killer cells. During treatment with IVIg or SCIg in CIDP patients, cellular immunomarkers were largely similar. CIDP patients receiving IVIg had higher macrophage inflammatory protein (MIP)‐1α (p = 0.01), interleukin (IL)‐4 (p = 0.04), and IL‐33 (p = 0.04) levels than SCIg recipients. IVIg treatment more broadly modulated cytokines in CIDP than SCIg treatment. Conclusions: Our study demonstrates that the modulation of cellular immunomarkers in CIDP is independent of the application route of therapeutic immunoglobulin. Minor differences were observed between CIDP and CVID patients. In contrast, cytokines were differentially modulated by IVIg and SCIg in CIDP. [ABSTRACT FROM AUTHOR]

Background and purpose: The gut microbiome is involved in autoimmunity. Data on its composition in chronic inflammatory demyelinating polyneuropathy (CIDP), the most common chronic autoimmune disorder of peripheral nerves, are currently lacking. Methods: In this monocentric exploratory pilot study, stool samples were prospectively collected from 16 CIDP patients (mean age 58 ± 10 years, 25% female) before and 1 week after administration of intravenous immunoglobulin (IVIg). Gut microbiota were analyzed via bacterial 16S rRNA gene sequencing and compared to 15 age‐matched healthy subjects (mean age 59 ± 15 years, 66% female). Results: The gut microbiota of CIDP patients showed an increased alpha‐diversity (p = 0.005) and enrichment of Firmicutes, such as Blautia (p = 0.0004), Eubacterium hallii (p = 0.0004), or Ruminococcus torques (p = 0.03), and of Actinobacteriota (p = 0.03) compared to healthy subjects. IVIg administration did not alter the gut microbiome composition in CIDP in this short‐term observation (p = 0.95). Conclusions: The gut microbiome in IVIg‐treated CIDP shows distinct features, with increased bacterial diversity and enrichment of short‐chain fatty acid producing Firmicutes. IVIg had no short‐term impact on the gut microbiome in CIDP patients. As the main limitation of this exploratory pilot study was small cohort size, future studies also including therapy‐naïve patients are warranted to verify our findings and to explore the impact of long‐term IVIg treatment on the gut microbiome in CIDP. [ABSTRACT FROM AUTHOR]