Guanosine and its modified derivatives are endogenous ligands for TLR7.

Toll-like receptor (TLR) 7and 8 were considered to recognize single-strand RNA (ssRNA) from viruses. Although these receptors also respond to synthetic small chemical ligands, such as CL075 and R848, it remains to be determined whether these receptors sense natural small molecules or not. In the structure of human TLR8 (huTLR8) with ssRNA, there are two ligand-binding sites: one binds a uridine and the other binds an oligoribonucleotide (ORN). This finding demonstrates that huTLR8 recognizes degradation products of ssRNA, suggesting the presence of natural small ligands. We here show that TLR7 works as the sensor for guanosine (G)/2'-deoxyguanosine (dG) in the presence of ORN where ORN strengthens TLR7 interaction with G/dG. In addition, modified nucleosides such as 7-methylguanosine, 8-hydroxyguanosine (8-OHG) and 8-hydroxydeoxyguanosine (8-OHdG) activated TLR7 with ORNs. Importantly, 8-OHdG-a well-known oxidative DNA damage marker with unknown function-induced strong cytokine production comparable to G and dG both in mouse and human immune cells. Although 8-OHdG bound TLR7/ORN with lower affinity than dG did in isothermal titration calorimetry, administered 8-OHdG was metabolically more stable than dG in the serum, indicating that 8-OHdG acts on TLR7 as an endogenous ligand in vivo To address a role of G analogs in the disease state, we also examined macrophages from Unc93b1 (D34A/D34A) mice, which suffer from TLR7-dependent systemic inflammation, and found that Unc93b1 (D34A/D34A) macrophages showed significantly enhanced response to G alone or 8-OHdG with ORN. In conclusion, our results provide evidence that G, dG, 8-OHG and 8-OHdG are novel endogenous ligands for TLR7.

Multiple environmental antigens may trigger autoimmunity in psoriasis through T-cell receptor polyspecificity.

Introduction: Psoriasis is a T-cell mediated autoimmune skin disease. HLA-C*06:02 is the main psoriasis-specific risk gene. Using a Vα3S1/Vß13S1 T-cell receptor (TCR) from a lesional psoriatic CD8+ T-cell clone we had discovered that, as an underlying pathomechanism, HLA-C*06:02 mediates an autoimmune response against melanocytes in psoriasis, and we had identified an epitope from ADAMTS-like protein 5 (ADAMTSL5) as a melanocyte autoantigen. The conditions activating the psoriatic autoimmune response in genetically predisposed individuals throughout life remain incompletely understood. Here, we aimed to identify environmental antigens that might trigger autoimmunity in psoriasis because of TCR polyspecificity. Methods: We screened databases with the peptide recognition motif of the Vα3S1/Vß13S1 TCR for environmental proteins containing peptides activating this TCR. We investigated the immunogenicity of these peptides for psoriasis patients and healthy controls by lymphocyte stimulation experiments and peptide-loaded HLA-C*06:02 tetramers. Results: We identified peptides from wheat, Saccharomyces cerevisiae, microbiota, tobacco, and pathogens that activated both the Vα3S1/Vß13S1 TCR and CD8+ T cells from psoriasis patients. Using fluorescent HLA-C*06:02 tetramers loaded with ADAMTSL5 or wheat peptides, we find that the same CD8+ T cells may recognize both autoantigen and environmental antigens. A wheat-free diet could alleviate psoriasis in several patients. Discussion: Our results show that due to TCR polyspecificity, several environmental antigens corresponding to previously suspected psoriasis risk conditions converge in the reactivity of a pathogenic psoriatic TCR and might thus be able to stimulate the psoriatic autoimmune response against melanocytes. Avoiding the corresponding environmental risk factors could contribute to the management of psoriasis.

Use of intralesional blood to determine diffusible biomarkers from skin lesions.

BACKGROUND: Biomarkers provide beneficial information to make diagnoses and monitor the progression of many skin diseases. However, biomarkers produced by skin lesion may be too low at concentration to be detected in the systemic circulation. OBJECTIVE: To address whether intralesional blood (ILB) is advantageous to detect skin-derived biomarkers over circulation blood (CB) of patients with skin diseases. METHODS: ILB was collected as overflowing blood when a small incision was made in lesions of patients with mastocytoma and psoriasis. Concentrations of histamine and Human ß-Defensin 2 were determined by ELISA. IL-8 was measured using a cytometric beads array (CBA) kit. IL-8 levels in psoriatic lesions were assessed by immunohistochemical staining and quantitative (q) RT-PCR. MicroRNA levels were measured using qRT-PCR. RESULTS: Plasma histamine levels were increased in ILB of mastocytoma compared with those in CB. Patients with psoriasis showed increased levels of IL-8, ß-Defensin 2 in ILB as compared to those in CB. IL-8 levels in ILB correlated with local PASI scores and therefore reversed to those in CB after attenuation of psoriasis with treatment. Furthermore, ILB in psoriasis patients showed increased miR-203, which was highly expressed in psoriatic epidermis. CONCLUSION: ILB contains disease-specific biomarkers at higher concentrations than those in CB, and may be useful for diagnosis and monitoring the progression of skin diseases. Thus, this study illustrates the versatility of ILB with an easy accessibility of biomarkers of chemicals, proteins as well as nucleic acids for a myriad of diseases including inflammatory dermatoses and cancers.