Allergen-specific IgE and IgGd antibodies in atopic and normal dogs

Intradermal skin tests (IDSTs) were performed on 65 atopic and 24 normal do gs. The levels of allergen-specific IgE and IgGd antibodies were determined in serum samples by enzyme-linked immunosorbent assay (ELISA) using the sa me 12 allergens that were used in the IDST on normal dogs. The correlation between the levels of IgE and IgGd to Dermatophagoides farinae (DF) and Der matophagoides pteronyssinus (DP) was examined. The sensitivity, specificity and positive and negative predictive values of allergen-specific IgE and I gGd levels in the total dog population were also compared. Results were con sistent and reproducible for 9/12 allergens, but in the case of house dust, flea and Alternaria tenuis, a less discriminating standard curve and the f act that the negative control gave positive results, suggests non-specific binding and that these allergens are complex and should not be employed wit hout further purification. A high percentage of atopic dogs had positive ID STs and detectable IgE and IgGd antibodies to DE DP and house dust. Similar results were obtained in the normal dog population. There were significant correlations between allergen-specific IgE and IgGd levels to DF and DP. H owever, in contrast to IgE, allergen-specific IgGd in normal dogs was highe r than in atopic dogs. Furthermore, a high percentage of the atopic populat ion had detectable IgGd to unrelated allergens, despite negative IDSTs. Ove rall, the negative predictive values were similar for both IEE and IgGd. Se nsitivities were higher in the allergen-specific IgGd assays, but the speci ficities and positive predictive values were higher in the allergen-specifi c IgE assays. In conclusion, the concordance of IDSTs with ELISA results to DF and DP in normal dogs without clinical signs implied the possible heter ogeneity of IgE in dogs. The presence of IgGd directed against apparently i rrelevant allergens in atopic patients and the high levels of IgGd in norma l dogs to the most common allergens, DF and DP, implied an uncertain role o f IgGd in canine atopic disease. Therefore, the detection of allergen-speci fic IEE is a more useful adjunct to the diagnosis of atopic disease in the dog than IgGd. (C) 1998 Elsevier Science B.V. All rights reserved.