588 Correlation between autologous serum skin test and levels of autoantibodies to FcεRI on mast cell in Japanese patients with chronic spontaneous urticaria S Izaki 1 , K Hayama 1 , D Fujisawa 1 , H Fujita 2 , C Ra 3 , Y Okayama 3 and T Terui 1 1 Department of Dermatology, Nihon University School of Medicine, Tokyo, Japan, 2 Department of Dermatology, Nihon University School of Medicine, Tokyo, Japan and 3 Allergy and Immunology Group, Nihon University School of Medicine, Tokyo, Japan Background: Anti-FcεRIa and anti-IgE antibodies have recognized to be related with auto- immune chronic spontaneous urticaria (CSU). The in vivo autologous serum skin test (ASST) is widely used to detect autoreactivity in autoimmune CSU, but its meaning is controversial. Objective: To recomfirm whether the ASST correlate the titer of anti-FcεRIa and anti-IgE antibody, disease severity, and effect of cycrosprine in CSU patients. Methods: We performed ASST in 61 CSU patients. Sera from patients and saline as a negative control were injected intradermally to forarms. The wheal response was measured at 30 min after injections, and was taken to be positive when the diameter of wheal is 2 mm bigger than that with saline. Disease severity was evaluated by Urticaria Activity Score (UAS) 7. Anti-FcεRIa antibody or anti-IgE antibody was detected by ELISA. Results: Twenty five out of 61 CSU patients were positive for ASST. The levels of anti-FcεRIa antibody and improvement of UAS7 with oral cycrosporine were significantly higher in ASST positive patients compared to negative patients (P¼ 0.0294, P¼0.00179), and there was no significant diffrence in levels of anti-IgE antibody in both groups (P¼0.189). Conclusions: These findings suggest that detection of anti-FcεRIa antibody may substitute ASST to predict the efficacy of cycrosporine for CSU patients. 589 Mechanisms of antitumor immunity by intralesional Mycobacterium bovis Bacillus Calmette-Guerin (BCG) in cutaneous melanoma metastases R Lardone 1 , A Chan 2 , A Lee 3 , L Foshag 3 , M Faries 3 , P Sieling 4 and DJ Lee 2 1 JWCI, Cordoba, Cordoba, Argentina, 2 Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, 3 JWCI, Santa Monica, CA and 4 NantBioscience, Culver City, CA Intralesional (IL) therapy using Mycobacterium bovis Bacillus Calmette-Gue ´rin (BCG) has been a relatively inexpensive option for treating inoperable cutaneous metastatic melanoma in NCCN guidelines for decades. Mechanisms of IL-BCG used in this manner have not been studied in the skin. We investigated the tumor microenvironment from melanoma patients combined with in vitro studies to further investigate pathways altered by BCG. Since mac- rophages play a pivotal role in defense against both cancer and mycobacterial infections, we hypothesized BCG can regulate macrophages to promote antitumor immunity. Tumor- associated macrophages (also known as M2) infiltrate solid tumors and impair antitumor immunity. BCG-treated, in vitro-polarized M2 (M2-BCG) show dramatic transcriptional changes involving inflammation, immune cell recruitment, cross-talk and activation path- ways. Mechanistic network analysis indicates potential for M2-BCG to improve IFN-g responses, frequently used as a marker for successful antitumor immunity. Accordingly, we found an increased frequency of IFN-g-producing CD4+ T cells responding to M2-BCG vs. mock-treated M2 (ppIn vitro BCG-infected cell lines derived from metastatic melanoma patients stimulated a higher frequency of IFN-g producing-TIL from the same melanoma patient (p < 0.05) than uninfected cell lines. Together, our data suggests BCG promotes an antitumor response in cutaneous metastatic melanoma through indirect and direct effects on the cell types within the tumor microenvironment including macrophages, T cells and the tumor itself. 590 Neutrophil extracellular traps exacerbate the inflammation in psoriasis by inducing CXCL1/CXCL10 secretion in keratinocytes S Shao 1 , H Fang 2 , E Dang 3 and G Wang 4 1 Xijing Hospital, The Fourth Military Medical University, Xi’an, Shanxi, China, 2 Xijing Hospital, The Fourth Military Medical University, Xi’an, Shaanxi, China, 3 Xijing Hospital, the Fourth Military University, Xi’an, Shaanxi, China and 4 Xijing Hospital, Xi’an, Shaanxi, China Neutrophil activation by inflammatory stimuli and the release of extracellular chromatin structures (neutrophil extracellular traps-NETs) have been implicated in the development of chronic inflammation and autoimmunity. However, whether and how NETs contribute to the pathogenesis of psoriasis is still not clear. Herein, we demonstrated that depleting neutrophils with neutralizing antibody dramatically alleviated the epidermis thickness and the infiltration of immune cells in psoriasis-like imiquimod-treated mice, which can be reversed by sub- cutaneous injection of NETs. Besides, inhibiting the formation of NETs with PAD4 inhibitor decreased the psoriasis-like inflammation significantly in imiquimod-treated mice. In vitro experiments showed that NETs activated primary human keratinocytes, leading to the high gene and protein expressions of cytokines and chemokines, especially CXCL1 and CXCL10, through NFkb and STAT3 activation. In addition, NETs-induced CXCL1 and CXCL10 pro- moted the chemotactic migration of T cells and neutrophils. The above findings were further supported by the detection of NETs in close proximity to keratinocytes in psoriatic lesions. And patients with psoriasis had increased plasma levels of NET components compared with controls. We also found that psoriasis-related agents, such as IL17A, TNF-a IFN-g, HMGB1 and LL37, could induce the formation of NETs in vitro. Taken together, these data suggest that NETs form in the serum and skin lesions of psoriasis patients and imiquimod-induced mice. NETs regulate the keratinocyte activation, resulting in the chemotaxis of T cells and neu- trophils, and might be targeted to reduce the inflammation in psoriasis. 591 Ultraviolet radiation alters the skin microbiome composition H Ahmed 1 , C Morrow 2 , N Yusuf 2 , HW Lim 3 , I Hamzavi 3 , E Burns 2 , A Shaheen 2 , A Muzaffar 2 , M Abdelgawwad 2 , C Al-Sadek 2 , T Foy 2 , R Kumar 2 , T Ptacek 2 , S Huda 2 , P Isedeh 3 and I Kohli 3 1 Florida State University, Orlando, FL, 2 University of Alabama at Birmingham, Birming- ham, AL and 3 Henry Ford Hospital, Detroit, MI The skin is home to microorganisms that tend to have commensal relationships with the host. As its own ecosystem, human skin and its microbiome are subject to the effects of environ- mental stressors, such as ultraviolet radiation (UVR). Knowledge of how the colonization of skin changes following this exposure can advance our understanding of the delicate balance between host and microorganism. We hypothesized that the cutaneous microbiome will change following exposure to UVR. To assess this, participants with Fitzpatrick types 1 and 2 were exposed to varying doses of UVA and UVB, immediately or after 24 hours. Swab samples were taken from the non-exposed/exposed sites and 16S ribosomal DNA bacterial gene sequencing was performed to identity the microorganisms present. We found that alteration in microbiome composition occurred following each UV dose, and not a single sample returned to the original pre-UVR composition. Following UVR, an overall decrease in composition of Lactobacillaceae and Pseudomonadaceae, while an increase in phylum Cyanobacteria were observed. These findings reveal a link between UVR and microbiome composition and may provide useful information for developing novel treatments in pre- venting sun damage or dermatologic conditions that may be caused or facilitated by host- microbe interactions. 592 RIG-I antiviral signaling drives interleukin-23 production and psoriasis-like skin disease H WANG Shanghai Jiao Tong University School of Medicine, Shanghai, China Retinoic acid inducible-gene I (RIG-I) detects short dsRNA and stem-loop RNA species bearing a 5’-triphosphate end, and functions as one of the major sensors of RNA viruses (Myong, Cui et al., 2009, Pichlmair, Schulz et al., 2006). DDX58, which encodes the RIG-I protein has been newly identified as a susceptibility gene in psoriasis, a chronic inflammatory skin disorder affecting the skin in 1-3% of the general population (2009, Tsoi, Spain et al., 2012). Recently, interleukin (IL)-23 has been demonstrated as a key master cytokine that promotes T helper 17 (Th17) cell survival and proliferation, and targeting the IL-23p19 sub- unit with a monoclonal antibody results in the clinical improvement in psoriasis (Kopp, Riedl et al., 2015, Zheng, Danilenko et al., 2007). Yet what triggers IL-23 production in the skin of individuals genetically predisposed to develop psoriasis is still unclear. Here, we show that RIG-I expression is increased in the affected skin derived from psoriasis patients and from IL-23-induced mouse model of psoriasis. The activation of RIG-I by 5’ppp-dsRNA, its syn- thetic ligand, directly causes the production of IL-23 and promotes chronic cutaneous inflammation in mice that closely resembles human psoriasis. Repeated injections of IL-23 to the ears failed to induce IL-23 production and a full psoriasiform skin phenotype, both in germ-free and RIG-I knockout mice. Furthermore, RIG-I-mediated IL-23 production was confined to the CD11c + myeloid dendritic cells (mDCs) via nuclear factor-kappa B (NF-kB) signaling, and stimulated RIG-I expression in an auto-regulatory feedback loop. Thus, our data suggest that the RIG-I-mediated antiviral response is pivotal for the local IL-23 pro- duction in the mDCs and for the IL-23-induced psoriasiform skin inflammation in mice, supporting the notion that dysregulation in the antiviral immune responses of hosts through the innate pattern-recognition receptors may trigger the skin inflammatory conditions in the pathophysiology of psoriasis. 593 Staphylococcal enterotoxin B modifies ovalbumin-induced innate immune responses and skin inflammation in a murine model of atopic dermatitis S Fassbender 1 , F Opitz 2 , S Johnen 2 , I Foerster 2 and H Weighardt 2 1 IUF Leibniz Research Institute for Environmental Medicine, Duesseldorf, Nordrhein-Westfalen, Germany and 2 LIMES Life and Medical Sciences Institute, University of Bonn, Bonn, Nordrhein-Westfalen, Germany Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by recurrent pruritic eczemas. Patients are at risk of staphylococcal infection, especially on lesional skin. Staphylococcus aureus-derived superantigens trigger disease progression and correlate with disease severity. To analyze the impact of superantigens to innate immune activation in AD we induced murine AD-like inflammation via repeated tape-stripping and subsequent sensitization to ovalbumin (OVA), staphylococcal superantigen B (SEB) or both and addressed the contribution of the innate immunity signaler MyD88 to AD pathogenesis. We could show that SEB itself induces mild, largely MyD88-dependent dermatitis symptoms. The combined sensitization to OVA+SEB boosted OVA-specific inflammation, Th1 and Th2 cytokine pro- duction and humoral immunoglobulin responses. While the expression of CCL17 and CCL22, as well as the Th2 induced immune response was MyD88-independently boosted by SEB, MyD88 was critically involved in the recruitment of epidermal CD8 + T cells to the inflamed skin and the induction of Th1 immunity. Collectively, our data emphasizethat SEB aggravates AD-like inflammation via several mechanisms including its superantigenic function or by acting as an antigen itself but also by interference with pathways of the innate immune system. ABSTRACTS | Innate Immunity, Microbiology, Inflammation S102 Journal of Investigative Dermatology (2017), Volume 137