Salivary fibronectin in man: an immunoblotting, radioimmunoassay and immunohistochemical study.

An antiserum and monoclonal antibody against plasma fibronectin recognized a 230-kDa, intact fibronectin molecule when 1000-fold diluted human plasma was subjected to immunoblot analysis. Immunoblot analysis of the parotid saliva demonstrated that the rabbit antiserum to human plasma fibronectin bound to five molecules (200, 110, 85, 75 and 65 kDa), other than the 230-kDa, intact fibronectin molecule, while the mouse monoclonal antibody recognized only the 230-kDa molecule. The 230-kDa type was not found in whole saliva with either the antiserum or monoclonal antibody. The antiserum reacted with 85-, 75- and 33-kDa molecules, and the monoclonal antibody recognized 75-, 33- and 20-kDa molecules in the whole saliva. Radioimmunoassay revealed that the mean +/- SD of fibronectin concentration in parotid saliva was 2.5 +/- 1.4 ng/ml (n = 20) and 149.8 +/- 46.2 ng/ml (n = 30) for whole saliva. Immunoperoxidase staining with rabbit antiserum and the mouse monoclonal antibody showed positive cytoplasmic staining of cells in the intralobular and interlobular ducts in parotid, submandibular, and sublingual glands. No acinar cells were stained.