027 Identification of a gain-of-function STAT3 mutation (p.Y640F) in lymphocytic variant hypereosinophilic syndrome

025 Recognition of mammalian and microbial lipid antigens by human T cells H Jiang, W Zeng, S Cremers and A de Jong 1 Dermatology, Columbia University, New York, NY, 2 Pathology and Cell Biology, Columbia University, New York, NY, 3 Medicine, Columbia University, New York, NY and 4 Irving Inst Clin Transl Research, Columbia University, New York, NY The lipids in human stratum corneum and sebum provide a physical barrier that protects against external microbial threats and prevents the loss of water and minerals. We have recently shown that beyond providing a physical barrier, skin lipids also have an immunological role. We identified certain classes of skin lipids, including waxesters, fatty acids, squalene and triglycerides, that can bind to the lipid antigen presenting molecule CD1a and be presented to T cells. CD1a is constitutively expressed at high levels on Langerhans cells, which are located at the interface of the skin lipidome and the skin immune system, supporting an important role for lipid antigen presentation in the skin. Since human skin is colonized by bacteria and fungi that contribute both indirectly (through lipase activity) and directly (through the release of microbial lipids) to the pool of lipids in the skin, an important question is whether CD1a-restricted T cells in the skin can distinguish lipids harboring mammalian fatty acid chains from structurally related lipids that harbor microbe-specific fatty acids chains (e.g methyl branched fatty acids). We are first determining if CD1a preferentially binds microbial fatty acid chains, and secondly, if CD1a-restricted T cell receptors preferentially bind complexes of CD1a with microbial lipids. We have developed and validated a HLPC/MS method to quantify relative amounts of structurally related mammalian and microbial fatty acid structures eluted from CD1a molecules, to determine their lipid binding preference. In addition, we are screening reactivity of T cells isolated from normal human skin against mammalian lipids and microbial analogs loaded onto plate-bound CD1a. Our studies will provide insights in how shifts in the composition of the skin lipidome, which occur in many skin diseases (e.g. atopic dermatitis, psoriasis), affect the activation of lipidspecific T cells in the skin. 026 Boosting of the delayed-type hypersensitivity response to varicella-zoster virus antigen following zoster vaccination in ageing individuals is associated with a local reduction in regulatory T cells N Patel, D Sandhu, M Vukmanovic-Stejic, M Rustin and A Akbar 1 Infection u0026 Immunity, University College London, London, United Kingdom and 2 Dermatology, Royal Free London NHS Foundation Trust, London, United Kingdom Ageing is accompanied by an increased risk of varicella-zoster virus (VZV) reactivation and impairment of the delayed-type hypersensitivity (DTH) response to VZV skin test antigen. The aim of this study was to investigate how the live attenuated zoster vaccine alters the kinetics of the DTH response to VZV antigen in old individuals. Healthy volunteers (n1⁄427, age range 70-93 years) were skin-tested with VZV antigen and those with a robust clinical response (2 individuals) were excluded from further participation, with a further 4 drop-outs. Numbers and proliferation (Ki67) of CD4 effector T cells and CD4 Foxp3 regulatory T cells at the test site were assessed by immunofluorescence microscopy at Days 1, 3 and 7 after VZV challenge. Volunteers were vaccinated after 4 weeks and repeat skin testing and immunofluorescence microscopy analysis were performed after a further 2-8 months. Overall, zoster vaccination led to a significant boost in clinical responses (p1⁄40.0002), although in 8 individuals there was no improvement. At Day 7 post-VZV challenge the median number of CD4 T cells per dermal perivascular infiltrate was significantly increased in vaccinated (40.0) compared with unvaccinated individuals (18.9, p1⁄40.026). The median percentage of proliferating CD4 T cells at Day 7 was 9.4% in the vaccinated compared with 4.0% in the unvaccinated (p1⁄40.162). At Day 7 the median proportion of CD4 T cells with a regulatory phenotype (Foxp3) reduced from 19.5% in the unvaccinated to 14.0% in the vaccinated (p1⁄40.088). This study demonstrates that the zoster vaccine significantly boosts the memory CD4 T cell response to VZV skin challenge in the old, partially restoring the intensity of the immune response to that seen in the young. Reduced inhibitory signalling as a consequence of fewer local regulatory T cells may be a possible mechanism underlying this vaccineinduced immune enhancement.