Influence of allergen-specific immunotherapy on allergen-specific IgG subclasses in dogs with atopic dermatitis

Abstract

Canine atopic dermatitis (AD) is one of the most common pruritic skin diseases in dogs and is diagnosed based on compatible history, clinical signs and exclusion of other pruritic skin diseases. Allergen-specific immunotherapy (ASIT) is widely used to treat AD but the precise mechanism of action is unknown. The aims of our study were to investigate the influence of ASIT on levels of Dermatophagoides farinae (D. farinae) specific IgG (D. farinae-IgG) subclasses and to explore whether changes in IgG subclasses are associated with the efficacy of ASIT. Sera from 98 dogs were collected before and during ASIT (duration of at least 2 years) with D. farinae. All dogs had serum IgE specific for D. farinae (imovet bg assay). Atopic dogs were divided into two groups: ASIT Group (n=48, ASIT as the sole therapy) and ASIT+ Group (n=50, insufficient control with ASIT requiring additional glucocorticoid treatment). A control group (CTRL Group, n=32) consisted of dogs without dermatological disease. Allergen-specific IgG subclass antibodies were detected by ELISA using monoclonal antibodies specific for canine IgG1 – IgG4. D. farinae-IgG1 and IgG4 were detected in >78% of all sera before ASIT while D. farinae-IgG2 and IgG3 were found in < 31%. Prior to therapy, dogs from the ASIT Group had significantly higher serum D. farinae-IgG1 than dogs in the ASIT+ Group (p<0.05). ASIT led to a significant increase in D. farinae-IgG1 in dogs from the ASIT (p<0.05) and ASIT+ (p<0.01) groups. D. farinae-IgG2, IgG3 and IgG4 concentrations were comparable for all groups before and during ASIT. Allergen-specific IgE concentration was not influenced by ASIT and the concentrations of IgG1 and IgG4 specific to an irrelevant antigen (Betula; birch pollen) were not influenced by ASIT against D. farinae. We conclude that long term ASIT increases levels of D. farinae-IgG1 and that dogs responding well to ASIT have a higher D. farinae-IgG1 concentration before therapy than partial responders.