Cellular Aspects of Cutaneous Inflammation: Clinical and in vitro studies of allergie contact dermatitis and allergie drug eruptions

This thesis is about the application of immunological insights and techniques to improve diagnosis, treatment and follow-up of inflammatory skin diseases, like allergic contact dermatitis (ACD) and allergic drug eruptions (ADE). The cells and mediators involved in cutaneous inflammation, allergic skin reactions in particular, will be discussed below. In chapter 1.2 and 1.3, clinical, epidemiological and immunological aspects of ACD and ADE, respectively, will be discussed. Finally, the various immunological techniques used in this thesis will be summarized in chap· ter 1.4. Healthy, uninflamed skin, with the horny layer as the first barrier, protects the body from loss of cells, fluids and electrolytes and from penetration of harmful substances like chemicals and infectious agents. In inflammatory skin conditions, such as psoriasis, contact allergy and wound healing, this barrier is disrupted or indi· rectly disturbed by an inflammatory infiltrate in the epidermis. Usually, inflammati on is an effective response. It is the basic reaction of living tissue to several types of injuries leading to its complete or incomplete healing. The classical signs of inflammation, irrespective of the tissue(s) involved, are rubor, calor, dolor, tumor and functio laesa, Le. redness, heat, pain, swelling and disturbed function, respectively. However, inflammatory skin disease may become 50 severe and widespread that it intervenes with physiological functions of the skin, like protection against external agents, prevention of water and heat loss, and, in a broader sense, psychosocial functions of the affected individu al. In inflammatory skin diseases, allergic skin reactions included, various resident, recruited and/or recirculating ce lis and their mediators participate. Together they constitute the Skin Immune System (SIS) [1, 2J. The SIS includes cells of the epidermis, the dermis, the blood vessels, the Iymphatics, and their mediators. The cutaneous nervous system interacts with several of these components of the SIS. The various constituents mentioned will now be looked at more closely in the following sections

Enhanced production of biologically active interleukin-1α and interleukin-1β by psoriatic epidermal cells ex vivo: Evidence of increased cytosolic interleukin-1β levels and facilitated interleukin-1 release

The expression of interleukin (IL)-1 is altered in psoriatic lesions. However, little is known about the actual production of IL-1α and IL-1β by psoriatic epidermal cells (EC). We monitored IL-1 in the extracellular, the membrane and the intracellular compartment of freshly isolated EC from untreated lesional psoriatic (PP) and normal healthy (NN) skin during non-stimulated short-term cultures, representing a psoriasis model ex vivo. Cytokines were measured using bioassays combined with neutralizing antibodies and enzyme-linked immunosorbent assay in parallel. PP EC released significantly increased amounts of biologically active IL-1α and IL-1β in a ratio of 3:1, whereas NN EC only released IL-1α. Also, the release of IL-6, but not of TNF-α, by PP EC was significantly increased. Membrane-associated IL-1 activity, analyzed using glutaraldehydefixed EC, was low and not unique to PP EC. The cytosol of PP EC contained significantly increased levels of immunoreactive IL-1β. Furthermore, PP EC displayed loss of membrane integrity, as determined by trypan blue exclusion and release of cytosolic lactate dehydrogenase. This facilitated release of intracellular IL-1. Depletion of CD45+ cells showed that intraepidermal leukocytes did not contribute to the production of IL-1. Our observations show that resident PP EC express enhanced IL-1 production ex vivo, which is due to an increased cytosolic IL-1β content and facilitated IL-1 release. This study provides the first evidence that PP EC can produce bioactive IL-1β