Immunohistochemical localisation of tear lipocalin in human nasal mucosa

Lipocalins are low molecular weight soluble proteins, a sub-class of this family are the odorant binding proteins (OBPs) which are postulated as having an important role in the perireceptor events of olfactory transduction, though their specific physiological function has yet to be defined. From the nasal mucus of normal subjects we recently isolated a 19kDa protein, the amino-acid sequence of which, limited to the first 20 residues, is identical to that of tear lipocalin. In this study we performed an immuno-histochemical investigation on the nasal localisation of this protein, using tissue specimens taken from the inferior (27 samples), middle (7 samples) and superior turbinates (6 samples) in 27 patients undergoing septoplastic surgery. The protein was detected in the sub-epithelial tubulo-acinar glands of the nasal mucosa, particularly in the mucoserous glands, in 74% of the specimens taken from the inferior turbinate, in 71.4% of those from the middle turbinate and in 66.6% of the samples of superior turbinate tissue. The homogeneous distribution of this protein in the nasal mucus could imply that it functions as a general protection agent rather than as an odour carrier or transducer.