376 Grass pollen-specific immunotherapy entails systemic increase of regulatory B cells and shift in Th17 cell compartments

Abstract

376 Grass pollen-specific immunotherapy entails systemic increase of regulatory B cells and shift in Th17 cell compartments CA Jakwerth, UM Zissler, FM Gurth, Z Hajdu, C Schmidt-Weber and AM Chaker 1 ZAUM Center of Allergy and Environment, Technische Universitat Munchen (TUM) and Helmholtz Center Munich, Member of the German Center for Lung Research (DZL), Munich, Germany and 2 ENT-Department, Klinikum rechts der Isar der Technischen Universitat Munchen (TUM), Munich, Germany IL-10-producing regulatory B cells (Bregs) are known to maintain regulatory capacities of T cells while restricting Th1 and Th17 differentiation. Recently, it has been shown that regulatory T cells (Tregs) can not only differentiate into effector Th17 cells via an intermediate subset expressing FoxP3 and IL-17 simultaneously, but also, that Th17 cells carry the ability to transdifferentiate “back” into Tregs. In this study, we extracted peripheral blood monocytes (PBMCs) from 20 allergic patients at several time points during an up-dosing period of grasspollen specific immunotherapy (SIT) and analyzed immune cell populations using flow cytometry. We prospectively monitored these patients over several years and collected further samples in and out of grass pollen season. Systemic Tand B-cell subsets were compared at baseline and six hours after the last maintenance top dose of SIT. We found a significant increase in IL-10-producing Bregs shortly after the last maintenance injection. On top, the IL10/TNF-a ratio in B cells was significantly increased, which has been postulated to indicate their regulatory function even stronger than IL-10 production alone. The increased Breg population in the blood coincided with a significant decrease of effector Th17 cells and, notably, with a decrease in the IL-17-expressing CD4FoxP3 Treg population. We postulate that the SIT-triggered induction of Bregs leads to a shift of Th17 cells towards a rather regulatory phenotype, as not only the Th17 population, but also the intermediate IL-17FoxP3 Treg subset was significantly decreased shortly after the last maintenance injection. In conclusion, the frequency of Th17 cells and IL-17-producing regulatory T cells in the peripheral blood may represent early biomarkers of immunotherapy efficacy. 377 IL-17E favors the recruitment of neutrophils in psoriasis via macrophage activation L Senra, R Stalder, W Boehncke and N Brembilla Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland Psoriasis vulgaris is a chronic recurrent inflammatory skin disease, affecting approximately 2% of the population. We have recently found that IL-17E (also known as IL-25), a member of the IL-17 cytokine family, is over-expressed in lesional psoriatic skin when compared to non lesional and healthy donors. Within the psoriatic plaque, macrophages represent an important proportion of IL-17E+ cells infiltrating the dermis. In this study we investigated the biological effects of IL-17E on macrophages in psoriasis. By confocal analysis of the lesional skin form 6 psoriatic patients, we found that IL-17E co-localized in macrophages with its receptor IL-17RB and clathrin, suggesting its in vivo internalization via a receptor-induced clathrin-mediated mechanism. Phenotypically, IL-17E+ macrophages exhibit a mixed M1/M2 phenotype, being positive for both CLEC5A and CD163L1 markers. In vitro, monocytederived macrophages were unable to produce IL-17E mRNA and internalized the cytokine in a time-dependent manner. The internalization process was blocked in the presence of a clathrin specific inhibitor. M2-polarized macrophages, but not M1, expressed high level of IL17RB and responded to IL-17E dose-dependently by increasing the mRNA levels of inflammatory cytokines and chemokines preferentially favoring the recruitment of neutrophils. Of note, the number of IL-17E+ cells in lesional skin correlated with the PASI score and the number of neutrophils, while being inversely proportional to the number of infiltrating T cells. In vivo, intra-dermal injection of rmIL-17E in C57BL/6 mice induced severe dermal inflammation with neutrophil and eosinophil infiltration, in addition to a hyperplastic epidermis, compared to the PBS control group. Our data provide strong evidence for a novel pro-inflammatory role of IL-17E in psoriasis, possibly via activation of macrophages leading to a preferential recruitment of neutrophils.