The cutaneous innate immune response in patients with atopic dermatitis  I-Hsin Kuo, MS, Takeshi Yoshida, PhD, Anna De Benedetto, MD, Lisa A. Beck, MD  Journal of Allergy and Clinical Immunology  Volume 131, Issue 2, Pages 266-278 (February 2013) DOI: 10.1016/j.jaci.2012.12.1563 Copyright © 2013 American Academy of Allergy, Asthma & Immunology Terms and Conditions

Fig 1 The skin as an impenetrable shield. The SC is the first physical barrier protecting the skin from the environment. Once this barrier has been breached, TJs found at the level of the stratum granulosum (SG) provide an additional barrier. Disruption of both physical barriers is thought to enable the uptake of allergens, irritants, and microbes by Langerhans cells (LC)/DCs. Keratinocytes produce AMPs as a chemical barrier in response to pathogen colonization/infection and tissue wounding to maintain skin homeostasis. The skin surface is colonized with a diverse array of microorganisms (microbiome barrier), which is thought to regulate local immune responses and to inhibit pathologic microbes. The itch-scratch cycle and cutaneous microbes first promote immune responses from keratinocytes and, only if needed, from a number of hematopoietic cells, including T cells, neutrophils (Neut cells), eosinophils (Eos), LCs/DCs, NK cells, and mast cells. Collectively, these cells constitute the cutaneous immunologic barrier. PRRs regulate the function of all of these barriers (physical, chemical, microbiome, and immunologic). SB, Stratum basale; SG, stratum granulosum; SS, stratum spinosum. The figure is modified from Swindle EJ, Collins JE, Davies DE. Breakdown in epithelia barrier function in patients with asthma: identification of novel therapeutic approaches. J Allergy Clin Immunol 2009;124:23-36. Journal of Allergy and Clinical Immunology 2013 131, 266-278DOI: (10.1016/j.jaci.2012.12.1563) Copyright © 2013 American Academy of Allergy, Asthma & Immunology Terms and Conditions

Fig 2 TLR2 and TLR3 are expressed below the TJs. Photomicrographs demonstrating the spatial relationship between TJs denoted by the presence of immunoreactivity for occludin (red) and 2 innate immune receptors highly relevant for AD (ie, TLR2 [left panel, green] and TLR3 [right panel, green]) are shown. Nuclei (4′-6-diamidino-2-penylindole dihydrochloride) are denoted by blue staining in these whole mounts of adult human epidermis (bars = 40 μm). In the bottom panel Z-stack images through the stratum granulosum (SG) to the stratum basale (SB) are rotated 90° (thickness = 15 μm). The image to the right summarizes the staining patterns and their intensity. Cell membrane expression of TLR2 is only observed below the TJs at the level of the stratum spinosum (SS) and SB. Faint cytosolic TLR2 immunoreactivity is observed in SG keratinocytes. The biologic significance of this intracellular staining is unclear. Similarly, the intracellular innate immune receptor TLR3 is found only in the cytoplasm of keratinocytes below the TJs (at the level of the SS and SB). Journal of Allergy and Clinical Immunology 2013 131, 266-278DOI: (10.1016/j.jaci.2012.12.1563) Copyright © 2013 American Academy of Allergy, Asthma & Immunology Terms and Conditions