Presence of Felis domesticus allergen I in the cat's salivary and lacrimal glands

Most of the IgE response in persons allergic to cats is directed against the cat allergen Fel d I (Felis domesticus allergen I). Although the presence of Fel d I in saliva has been demonstrated, the source of Fel d I is not completely known. We measured Fel d I concentrations in the cat's lacrimal and salivary glands and in the excretes lacrimal fluid, milk and saliva. The concentration of Fel d I, determined by a radioimmunoassay, in the lacrimal gland was 390-780 mU/g tissue and in the sublingual gland 610 mU/g tissue. In the parotid gland and especially the submandibular gland only low concentrations were found, respectively 70-210 and 40-50 mU/g tissue. In lacrimal fluid 6.8-14 U/ml Fel d I was detected, which is comparable to saliva, 4.2-7.0 U/ml, whereas in cat's milk only 0.33 U/ml Fel d I was found. Immunohistochemical studies with monoclonal antibody directed against Fel d I (anti-Fel d I) showed the presence of Fel d I in the serous cells of the lacrimal gland. Thus, our results demonstrate that in particular the lacrimal gland might be a useful Fel d I source.