Isolation of pemphigus antigen from human saliva.

Whole human saliva from six unrelated normal donors was found to contain a glycoprotein that reacts with pemphigus autoantibodies. Blocking of the indirect immunofluorescent staining produced by pemphigus antibodies from a patient serum on rat tongue epithelia was used to detect this pemphigus antigen. The amounts of this antigen in saliva appeared to be unrelated to HLA, red cell phenotype, or secretor status of the donors. Salivary pemphigus antigen was shown to be destroyed by either boiling or freezing and thawing and was preserved at 4°C in fractions previously treated with PMSF (2.8 mM) and stored in 0.01 M Tris/acetate buffer, pH 7.5, containing DTT (20 mM), CaCl2 (5 mM), and 0.14 M NaCl. The antigen is not dialyzable (greater than 10,000 m.w.). Salivary pemphigus antigen was isolated by gel filtration (Bio-Gel A 1.5 m and P-200) and affinity chromatography by using rabbit antisera made against contaminant salivary components. The antigen eluted immediately after albumin on gel filtration and showed a single band on alkaline PAGE. Unreduced SDS-PAGE of the antigen revealed two dense bands of approximately 20,000 and 25,000 daltons m.w., respectively, and a third faint band of 50,000 m.w. Reduced SDS-PAGE showed a thick band that could be resolved into the 20,000 and 25,000 m.w. components. Salivary pemphigus antigen is a glycoprotein that contains approximately 30% (w/w) carbohydrate. The origin of this pemphigus antigen in saliva and its immunochemical relationship with epidermal pemphigus antigen remain to be determined.