FcεRI stimulation promotes the differentiation of histamine receptor 1-expressing inflammatory macrophages.

BACKGROUND: Monocyte differentiation into dendritic cells or macrophages and recruitment to peripheral organs in chronic inflammatory diseases are directed by allergen challenge via FcεRI as well as the nature of soluble factors in the microenvironment. High-affinity receptor for IgE stimulation of effector cells results in the release of histamine, which acts on various histamine receptors (HR) 1-4, expressed by immune cells. METHODS: We examined the effect of FcεRI stimulation of human monocytes on H1R expression and function of differentiating cells. The mRNA levels of H1R, H2R and histidine decarboxylase of differentiating cells were detected by quantitative real-time PCR. Expression of CD1c, CD11c, CD68 and CD163 was detected by flow cytometry. Amount of histamine, IL-6 and IL-12p70 in the cell culture was measured with the help of cytometric bead arrays or ELISA assays. Numbers of H1R-expressing macrophages were evaluated by immunofluorescence double staining of CD68 and H1R on human skin sections. RESULTS: We demonstrated that FcεRI stimulation promotes the generation of H1R-expressing macrophage-like cells with enhanced histamine biosynthesis and H1R-mediated proinflammatory properties. Supporting our in vitro findings, high numbers of H1R-expressing CD68(pos) macrophages were detected in the dermis of atopic dermatitis (AD) skin lesions. CONCLUSION: Our observations point to a close histamine-/HR-mediated activation of dermal macrophages, leading to modified cell differentiation and responsiveness via H1R, which might contribute to the aggravation of allergic skin inflammation in AD.

Tolerogenic T cells, Th1/Th17 cytokines and TLR2/TLR4 expressing dendritic cells predominate the microenvironment within distinct oral mucosal sites.

BACKGROUND: Most local oral vaccine strategies use the sublingual region for drug application. Only little is known about the cytokine micromilieu, the nature of T cell subtypes and expression of target structures for adjuvants at different oral mucosal regions (OMR). However, targeting the optimal OMR might ensure highest efficiency of drug uptake and lowest risk for adverse effects. METHODS: Expression of TGF-ß1, IL10 as well as Th1, Th2 and Th17 cytokines and transcription factors was investigated at different OMR and skin by quantitative real-time PCR, immunohistochemistry or flow cytometry. RESULTS: Highest number of T cells was located in vestibular/buccal region (VBR). In contrast to skin (SK), OMR T cells produced TGF-ß1, IL-10, IFN-γ and IL-17. Significantly higher TGF-ß1 mRNA expression in the VBR compared with the sublingual region (SLR) and skin could be detected, while equal transcripts of IL-10 and regulatory T cell-associated transcription factor FoxP3 could be demonstrated. Expression of Th17-associated IL-17A, IL-17F, IL-22 and IL-26 mRNA could be demonstrated in VBR and SLR but not in SK. Interestingly, compared to SK, significantly higher expression of TGF-ß1 and IFN-γ could be detected in OMR. Moreover, expression of toll-like receptor (TLR) 2 and TLR4 was highest in VBR with significant expression on dendritic cells in OMR. CONCLUSION: From this data, we conclude that (i) VBR and SLR represent a protolerogenic micromilieu, (ii) both regions form a Th1 cytokine-predominated microenvironment, but also express mRNA for Th17 cytokines and (iii) TLRs detectable in VBR and SLR might serve as a target structures for adjuvants.

Tetraspanins CD9 and CD81 are molecular partners of trimeric FcɛRI on human antigen-presenting cells.

BACKGROUND: Most functions of tetraspanins are not related to cell-surface receptor ligand binding, but are mediated by direct interactions with their partner proteins. Functions of trimeric FcɛRI, expressed by antigen-presenting cells (APCs), range from amplification of allergic inflammatory reactions to their active suppression. Cell-type-specific protein-protein interactions might play a role in the regulation of these bidirectional tasks. Therefore, we intended to study the interactions of trimeric FcɛRI with tetraspanins. METHODS: The expression levels of tetraspanins CD9, CD37, CD53, CD63, CD81, CD82, and CD151 on skin dendritic cells of atopic dermatitis (AD) patients or healthy individuals were detected by flow cytometry. Tetraspanin expression on FcɛRI(pos) and FcɛRI(neg) monocyte subpopulations was evaluated. Flow cytometry, confocal microscopy, immunoprecipitation, and immunoblotting experiments were performed to observe the relationship between tetraspanins CD9 and CD81 and FcɛRI. Furthermore, plate stimulation experiments were performed, and cytokines in the supernatants were detected. RESULTS: We found that human FcɛRI(pos) APCs expressed high amounts of tetraspanins and that the tetraspanins CD9 and CD81 were associated with FcɛRI. Concomitant activation of FcɛRI and CD9 on human monocytes increased FcɛRI-mediated cytokine release. CONCLUSION: Taken together, we show for the first time that CD9 and CD81 act as molecular partners of trimeric FcɛRI on human APC, which might be of importance in allergic diseases such as AD.

Putative association of a TLR9 promoter polymorphism with atopic eczema.

BACKGROUND: Toll-like receptors (TLR) play a pivotal role in the induction of first-line defense mechanisms of the innate immune system and trigger adaptive immune responses to microbial pathogens. Genetic variations in innate immunity genes have been reported to be associated with a range of inflammatory disorders. Deficiencies on the level of immunity receptors such as pathogen-recognition receptors are suspected to affect the maturation of our immune system and to avail thereby the high prevalence of atopic diseases and susceptibility of atopic patients to microbial infections. AIMS OF THE STUDY: We evaluated TLR9 as susceptibility gene for atopic eczema (AE). METHODS: Analyses of four tag single-nucleotide polymorphisms in two panels of families containing a total of 483 parent-affected offspring trios as well as a cohort of 274 unrelated adult AE cases and 252 hypernormal population-based controls have been performed. RESULTS: In both family cohorts, polymorphism C-1237T, which is located within the promoter region of the TLR9 gene, was significantly associated with AE, in particular the intrinsic subtype of AE. No associations were seen in the case-control cohort. Luciferase reporter gene assays revealed significantly higher promoter activity of the TT allelic variant at this single nucleotide polymorphism site. CONCLUSION: These observations suggest that the TLR9 promoter polymorphism C-1237T might affect AE susceptibility in particular in patients with the intrinsic variant of AE.

Dancing with the enemy: the interplay of herpes simplex virus with dendritic cells.

Summary Herpes simplex virus (HSV) represents a smart pathogen, which displays both lytic and latent modes of interaction with its natural human host. In order to be optimally equipped for immune evasion and to reply to any attacks of the host during reactivation, HSV has developed a multitude of cleverly devised defence strategies. Dendritic cells (DC) as antigen-presenting cells located at the border zones of the body and the environment have been shown to play a crucial role as one of the first cells interacting with HSV beside epithelial cells, on one hand, and as important controllers of the viral spreading on the other hand. Here, we provide a research update about the interaction of HSV with DC and summarize the latest proceedings in this field.