Endogenous avidin-binding activity in epithelial cells of the ducts of human salivary glands.

Avidin-biotin (AB) systems are commonly employed to investigate salivary gland sections either in immunohistochemistry or in immunofluorescence techniques. We noted non-specific staining in the ductal epithelium of minor salivary gland (SG) sections from 5 Sjögren's syndrome (SS), 5 chronic sialoadenitis (CS), and one normal parotid gland (NP) when incubated with AB peroxidase complex. Inhibition of endogenous peroxidase did not prevent the staining while saturation of supposed biotin-like molecules in the tissue with added avidin led to the loss of this non-specific staining. These results demonstrate the presence of endogenous avidin binding activity (EABA) in the epithelial cells of salivary gland ducts. We suggest that the avidin and streptavidin systems should not be used for immunohistological examination of the ductal epithelium of salivary glands.