Class II MHC antigen expression on epithelial cells of salivary glands from patients with Sjögren's syndrome.

Class II MHC molecules are two-chain glycoproteins normally expressed only on the membrane of cells involved in the immune response. These molecules are restriction elements for helper T cells. Using indirect immunofluorescence on cryostat sections of biopsied salivary glands we have demonstrated epithelial expression of class II antigens in patients with Sjögren's syndrome. The HLA DR+ epithelial cells were seen in close proximity to lymphocyte infiltrates. The finding that class II molecules are also expressed in salivary glands without focal lymphocytic infiltrates suggests a "modulation" as opposed to "induction" of HLA DR antigens on epithelial cells in Sjögren's syndrome, the distinction being related to the enhancement of low levels of expressions vs. de novo synthesis.