OBJECTIVES To investigate the expression and regulation of CD80, CD86, and CD28 costimulatory molecules in sialoadenitis and interstitial nephritis in patients with Sjögren's syndrome (SS).

RESULTS In patients with severe sialoadenitis, CD80 and CD86 were strongly expressed on ductal epithelial cells. In contrast, these antigens were not found in the minor salivary glands of normal subjects or of patients with mild sialoadenitis. Some infiltrating cells expressed CD28. In patients who had interstitial nephritis associated with SS, some tubular epithelial cells expressed CD86 but not the CD80 antigen. Unstimulated HSG cells did not express CD80 or CD86. Interferon γ (IFNγ) consistently up regulated levels of CD80 and CD86. In contrast, tumour necrosis factor α (TNFα), interleukin 1β (IL1β), IL2, and IL4 had no effect on either CD80 or CD86 levels. Unstimulated HRCE did not express CD80 or CD86. IFNγ consistently up regulated CD86 expression. No CD80 expression was found on tubular cells. TNFα, IL1β, IL2, and IL4 had no discernible effects.

CONCLUSIONS Salivary ductal cells in patients with SS can express CD80 and CD86 costimulatory molecules in response to IFNγ. Tubular epithelial cells in patients who have interstitial nephritis associated with SS express only CD86 molecules. In patients with SS, salivary ductal cells and tubular epithelial cells may activate infiltrating CD28 positive T lymphocytes by presenting antigens to T cells, potentially leading to tissue destruction.