Toll-Like Receptor 8 is Expressed in Monocytes in Contrast to Plasmacytoid Dendritic Cells and Mediates Aberrant Interleukin-10 Responses in Patients With Systemic Sclerosis.

OBJECTIVE: Systemic sclerosis (SSc) is a severe rheumatic disease causing fibrotic tissue rearrangement. Aberrant toll-like receptor (TLR) 8 transcripts in plasmacytoid dendritic cells (pDCs) were recently linked to SSc pathogenesis, which is at least partially mediated by increased type I interferon (IFN-I) responses. Here, we addressed the functional role of TLR8 signaling in different immune cell subsets of patients with SSc. METHODS: Monocytes, conventional dendritic cells (cDCs), and pDCs from the blood and skin of patients with SSc were analyzed for TLR8 protein expression. To assess TLR function, cytokine responses upon TLR7 and TLR8 stimulation were studied. To identify relevant alterations specific for patients with SSc (n = 16), patients with primary Sjögren disease (pSS; n = 10) and healthy controls (HCs; n = 13) were included into the study. RESULTS: In all individuals, TLR8 was expressed in monocytes and cDCs but not in pDCs. The TLR8 expression levels were overall similar in patients with SSc and pSS and HCs. Additionally, in all study participants, TLR8 stimulation of pDCs did not induce IFN-I expression. In contrast, monocytes from patients with SSc revealed increased interleukin (IL)-10 responses upon TLR8 (patients with SSc vs HCs, P = 0.0126) and TLR7/8 stimulation (patients with SSc vs HCs, P = 0.0170). CONCLUSION: TLR8 protein is not expressed in pDCs of patients with SSc. Accordingly, they do not respond to TLR8 stimulation. In contrast, monocytes of patients with SSc respond to TLR8 stimulation with increased IL-10 responses. Therefore, TLR8 signaling in monocytes participates in SSc pathogenesis by conferring aberrant IL-10 expression.

Treatment of autoimmunity: The impact of disease-modifying therapies in multiple sclerosis and comorbid autoimmune disorders.

More than 10 disease-modifying therapies (DMT) are approved by the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA) for the treatment of multiple sclerosis (MS) and new therapeutic options are on the horizon. Due to different underlying therapeutic mechanisms, a more individualized selection of DMTs in MS is possible, taking into account the patient's current situation. Therefore, concomitant treatment of various comorbid conditions, including autoimmune mediated disorders such as rheumatoid arthritis, should be considered in MS patients. Because the pathomechanisms of autoimmunity partially overlap, DMT could also treat concomitant inflammatory diseases and simplify the patient's treatment. In contrast, the exacerbation and even new occurrence of several autoimmune diseases have been reported as a result of immunomodulatory treatment of MS. To simplify treatment and avoid disease exacerbation, knowledge of the beneficial and adverse effects of DMT in other autoimmune disorders is critical. Therefore, we conducted a literature search and described the beneficial and adverse effects of approved and currently studied DMT in a large number of comorbid autoimmune diseases, including rheumatoid arthritis, ankylosing spondylitis, inflammatory bowel diseases, cutaneous disorders including psoriasis, Sjögren´s syndrome, systemic lupus erythematosus, systemic vasculitis, autoimmune hepatitis, and ocular autoimmune disorders. Our review aims to facilitate the selection of an appropriate DMT in patients with MS and comorbid autoimmune diseases.

Congenital deficiency reveals critical role of ISG15 in skin homeostasis.

Ulcerating skin lesions are manifestations of human ISG15 deficiency, a type I interferonopathy. However, chronic inflammation may not be their exclusive cause. We describe two siblings with recurrent skin ulcers that healed with scar formation upon corticosteroid treatment. Both had a homozygous nonsense mutation in the ISG15 gene, leading to unstable ISG15 protein lacking the functional domain. We characterized ISG15-/- dermal fibroblasts, HaCaT keratinocytes, and human induced pluripotent stem cell-derived vascular endothelial cells. ISG15-deficient cells exhibited the expected hyperinflammatory phenotype, but also dysregulated expression of molecules critical for connective tissue and epidermis integrity, including reduced collagens and adhesion molecules, but increased matrix metalloproteinases. ISG15-/- fibroblasts exhibited elevated ROS levels and reduced ROS scavenger expression. As opposed to hyperinflammation, defective collagen and integrin synthesis was not rescued by conjugation-deficient ISG15. Cell migration was retarded in ISG15-/- fibroblasts and HaCaT keratinocytes, but normalized under ruxolitinib treatment. Desmosome density was reduced in an ISG15-/- 3D epidermis model. Additionally, there were loose architecture and reduced collagen and desmoglein expression, which could be reversed by treatment with ruxolitinib/doxycycline/TGF-ß1. These results reveal critical roles of ISG15 in maintaining cell migration and epidermis and connective tissue homeostasis, whereby the latter likely requires its conjugation to yet unidentified targets.

Eosinophil granulocytes: functional differences of a new isolation kit compared to the isolation with anti-CD16-conjugated MicroBeads.

BACKGROUND/PURPOSE: Using a new eosinophil isolation kit, we were not able to confirm our previous findings of a delayed apoptosis of eosinophils in atopic dermatitis. Thus, we investigated whether this new isolation kit modulates the functional activity of eosinophils. METHODS: Peripheral blood eosinophils were isolated with the new isolation kit as well as conventionally with anti-CD16-conjugated MicroBeads. We analysed viability, apoptosis, CD69 and CD95 expression, streptavidin binding and superoxide anion release. RESULTS: Purity of eosinophils was higher using the new isolation kit (P < 0.05). However, these eosinophils had a decreased survival (P < 0.05-0.01), presented morphological features of apoptosis, showed an increased percentage of apoptotic nuclei (P < 0.01), an increased release of superoxide anions (P < 0.05), a higher expression of CD69 and CD95 (P < 0.05) and an increased binding to streptavidin compared to eosinophils isolated with anti-CD16 conjugated MicroBeads. CONCLUSION: The new eosinophil isolation kit should not be used for the investigation of eosinophils as it potently affects their functional activity.