Skin as an immune organ and clinical applications of skin-based immunotherapy

BackgroundThe prevalence of food allergy is increasing, and allergen avoidance continues to be the main standard of care. There is a critical need for safe and effective forms of immunotherapy for patients with food allergy as well as other allergic diseases.FindingsThe skin is a multifunctional organ with unique immunologic properties, making it a favorable administration route for allergen-specific immunotherapy. Epicutaneous immunotherapy (EPIT) takes advantage of the skin's immune properties to modulate allergic responses and is thus one of the allergen-specific immunotherapy approaches currently being investigated for food allergy. Advances made in the understanding of how epicutaneously applied proteins interact with the immune system and in the technology for facilitating such interactions offer many opportunities for clinical application. Research has shown that allergen delivered to intact skin via EPIT is taken up in the superficial layers of the skin by Langerhans cells, avoiding passive movement of allergen through the dermis and limiting systemic circulation. EPIT brings about allergen desensitization by activating a population of regulatory T cells (Tregs) with unique properties and the potential for inducing a sustained effect as well as the possibility (seen in animal models) for protection against further sensitizations. Several clinical trials investigating the therapeutic efficacy of EPIT for treatment of peanut allergy have been completed, as well as a Phase 2 trial for treatment of milk allergy.ConclusionsTaken together, the reviewed literature supports the concept that EPIT activates the natural desensitization pathway of the skin, offering a progressive, possibly sustained response. EPIT offers a potential alternative for allergen immunotherapy that is less invasive and carries a lower risk for systemic reactions than oral immunotherapy.