Immunological differences in the global release of the major cat allergen Fel d 1 are influenced by sex and behaviour

The biological function of Fel d 1, the major cat allergen released in the environment, is still unclear despite studies suggesting a putative role in chemical communication. Structural and immunological polymorphisms of Fel d 1 have been described. This study examined how Fel d 1 immunological polymorphism may have a physiological origin by estimating a potential relationship with the sex of cats and cat–human interactions. Samples from bath washes of 21 cats were screened to study antibody binding to Fel d 1 using an ELISA. Personality and Tolerance Handling scores were used to assess the behaviour of the cats. washes, Fel d 1 concentrations were significantly lower in females than in males (P < 0.05). Slopes from the ELISA dose–dependent curves varied among the cats: males secreted Fel d 1 variants with higher antibody recognition than females (P < 0.01). Females that were aggressive and difficult to handle displayed a diminished slope value, and therefore a weaker Fel d 1 immunoreactivity in global washes, compared to females that were sociable (P = 0.09) and easy to handle (P = 0.07). This study shows a variable immunological polymorphism of Fel d 1 within a cat population, particularly between males and females, and this polymorphism appears to be related to cat–human interactions.