Review: Innate immunity, lipid metabolism and nutrition in canine atopic dermatitis.

Background: The pathogenesis of canine atopic dermatitis (AD) involves dysfunction of the adaptive immune system. Recent evidence suggests that nonantigen-specific inflammatory elements may play a role in the development and perpetuation of canine AD.

Objectives: The objective of this review is to provide an update on recent advances in the understanding of the role of innate immune cells, keratinocytes, lipid metabolism and nutrition in the pathogenesis of AD in dogs.

Methods: Citation databases, abstracts and proceedings from international meetings published between 2001 and 2013 are reviewed in this update. Where necessary, older articles are included for background information.

Results: Members of the innate immune system (including dendritic cells, Langerhans cells and mast cells) and keratinocytes interact with each other and with environmental antigens during both induction and effector phases of atopic inflammation. The responses of these cells and associated noncellular factors (such as complement and protease-activated receptors) to environmental stimuli influence the entire future course of the immune response to a given agent. Abnormalities in lipid metabolism may also influence the pathogenesis of canine AD via the production of inflammatory mediators and by alteration of epidermal barrier function and antigen presentation. However, a lack of fully controlled studies precludes definitive interpretation of these data.

Conclusions And Clinical Importance: Evidence indicates that the cells and noncellular components of the innate immune system and the epidermis may play critical roles during both the sensitization and the effector phases of canine AD. Derangements in lipid metabolism may be involved in the pathogenesis of AD in dogs, but additional controlled studies are required in this area.