IgE and IgG binding patterns and T-cell recognition of Fel d 1 and non-Fel d 1 cat allergens.

Background: Cat allergy affects approximately 15% of the population and is a major risk factor for asthma. The relative importance of cat allergens other than Fel d 1 is not known.

Objective: To compare IgE and IgG antibody binding and T-cell recognition of the major cat allergen Fel d 1 with other cat proteins with known IgE binding properties.

Methods: IgE, IgG1, and IgG4 antibody to Fel d 1, 2, 3, 4, 7, 8, and the undesignated IgE binding proteins haptoglobin and S100A12 were measured in the plasma of 96 individuals with cat allergy and 78 individuals without cat allergy. Cytokines were measured from T cells stimulated with the cat allergens.

Results: An allergen other than Fel d 1 had the highest IgE binding specificity for 35% of individuals with cat allergy, and it bound more than 50% of their IgE antibody in 70% of these sera. Fel d 4, 7, and 8 were identified as the main contributors to the non-Fel d 1 IgE binding response and elicited inflammatory Th2 cytokines to a similar degree as Fel d 1. As expected, the average percentage of IgE binding to Fel d 1 for individuals was 55%. IgG4 binding to Fel d 1 was detected in both subjects with allergy (30%) and subjects without allergy (19%). IgG4 binding to the other allergens was less prevalent but was found for both groups. IgG1 antibody was not detected to any of the newly described cat proteins.

Conclusion: Fel d 4, 7, and 8 are allergens that should be included in the diagnosis and investigation of cat allergy.