Expression of B7 costimulatory molecules by salivary gland epithelial cells in patients with Sjogren's syndrome

Objective. To investigate the expression of B7 costimulatory molecules in t he lymphoepithelial lesions of salivary gland (SG) biopsy tissues and in SG epithelial cell lines derived from patients with Sjogren's syndrome (SS). Methods. B7.1 and B7.2 protein expression was studied by immunohistochemist ry in minor SGs obtained from 11 patients with SS and 10 disease control pa tients with nonspecific sialadenitis and in cultured SG epithelial cell lin es obtained from minor SGs from 15 SS patients and 15 control patients. B7. 1 and B7.2 messenger RNA (mRNA) expression by SG epithelial cell lines was examined by reverse transcription-polymerase chain reaction (RT-PCR). Results. In biopsy tissues from SS patients, but not control patients, duct al and acinar epithelial cells showed increased expression of both B7.1 and B7.2, Intense spontaneous B7.1 protein expression las well as HLA-ABC, but not B7.2 or HLA-DR) was also found in 73% of SG epithelial cell lines from SS patients versus 13% of those from control patients (P < 0.01). Interfer on-gamma treatment induced, or up-regulated, B7.1, B7.2, and HLA-DR express ion in all SG epithelial cell lines tested. B7.1 and B7.2 expression by SG epithelial cell lines was also verified at the mRNA level by RT-PCR. Conclusion. Human SG epithelia are intrinsically capable of expressing B7 p roteins upon activation. In SS patients, the expression of B7 molecules by SG epithelial tissues and by SG epithelial cell lines indicates the activat ed status of SG epithelial cells in this disorder and, possibly, their capa city for presenting antigens to T cells.