To investigate the correlation between the differential expression of 60 000 SSA epitopes in minor salivary glands (MSG) from patients with primary Sjögren's syndrome (pSS) and glandular inflammation.
The screening and soluble expression of single-chain fragment V monoclonal antibodies (Scfv McAb) against SSA antigen epitopes (P1: 480 - 494, P2: 310 - 323 and P3: 230 - 241) were performed by phagemid antibody expression system. The expression of epitopes was detected by immunohistochemical assay (IH) in minor salivary glands from these patients. The correlation between epitopes expression and glandular inflammation was analyzed quantitatively.
Immunohistochemical assay of MSG with McAb against P1-P3 epitopes showed that the epithelial cells of glandular tubes and striated duct were stained in membrane and cytoplasm. The expression of P1 epitope was higher than the other two in grading score (chi(2) = 12.94, P < 0.01). And a positive correlation was found between the extent of glandular infiltration and the grade of P1 epitope expression (t = 2.27, P < 0.05) but not with P2 or P3 epitope.
Aberrant redistribution of intracellular SSA antigen epitopes onto the cell membrane of involved cells may break the immune tolerance and thus induce the production of pathogenic autoantibodies involved in triggering and maintaining the tissue-specific autoimmune response in pSS MSG. A significantly high membranous expression of P1 and a positive correlation between P1 and the inflammation of MSG suggest that P1 may be the dominant determinant of the antigen-driven immune response in pSS.