Comparison of the Influence of Different Skin Conditions on the Allergic Skin Reactivity to Epicutaneous Allergen Exposure

BACKGROUND INFORMATION The prevalence of allergic diseases has been continuously increasing, reaching a prevalence of up to 30% in industrialized countries. In Switzerland, about 2 million people are affected by IgE-mediated allergies as reported by the Swiss Center for Allergy, Skin and Asthma and the Swiss Society for Allergology and Immunology (SSAI). By subcutaneous injections of gradually increasing allergen doses, conventional subcutaneous SIT (SCIT) is found to reduce the inappropriate T-helper (Th) 2 responses and IgE production. Due to the risk of systemic allergic side effects, the typical therapy duration of 3-5 years and the requirement of 50-80 injections, patient acceptance of SCIT is low and less than 5% of allergy patients choose to undergo SCIT. A recently rediscovered route of allergen administration is via the epidermis in a procedure called epicutaneous immunotherapy (EPIT).

The skin is an attractive administration route for immunotherapy being both easily accessible as well as playing an important role in the immune system consisting of keratinocytes, Langerhans cells (LC), dermal dendritic cells (DC). A major challenge in EPIT is to overcome the physiological barrier function of the skin. In order to deliver the allergen to the immunological effector cells in the skin, the allergen must be transported through the outermost keratinized layer of the epidermis, called the stratum corneum. The stratum corneum is 10-20μm thick and impermeable for molecules greater than 500 Da. Proteins, such as allergens, do not passively permeate across the skin and therefore enhancement strategies are needed to enable this transfer. Advances in microtechnology might contribute to improve the situation by allowing for the miniaturization of mechanics and structures. As the stratum corneum is only 10-20μm thick, it has been proposed by Henry et al., that microneedles as small as a few tens to a few hundreds of microns, could be used to penetrate the stratum corneum.

Such new methods of overcoming the skin barrier raise the question of the influence of different types of skin injury patterns on the allergic skin reactivity. Namely, how important is the role of the exposed area (microneedles), the depth of injury (skin pricking) and the keratinocyte activation. This physiological question is in the focus of this study.

PRODUCTS In order to investigate the physiological reactions concerning different skin conditions and allergen exposition the following products/techniques have been chosen for the purpose of inducing different skin conditions in a reproducible way.

Prick lancet: