Epidermal cell surface-associated IgG in patients with primary Sjögren's syndrome: in vitro evidence for immune complex binding.

In vivo deposits of IgG have previously been demonstrated in the epidermal intercellular area of clinically unaffected skin from 68% of patients with primary Sjögren's syndrome (primary SS). This study compared circulating IgG from patients with primary SS with that from secondary SS in their ability to bind normal human epidermal cells in vitro. We observed a granular pattern of IgG binding to the normal epidermal cell surfaces with 9 of 18 sera from patients with primary SS (50%), 3 of 19 sera from patients with SS secondary to rheumatoid arthritis (16%) (p = 0.025), and none of 24 normal control sera (p less than 0.001). In a subsequent analysis of polyethylene glycol separated sera from two normal controls and two primary SS patients, the epidermal IgG binding capacity was found only in the precipitates of the patients. These findings support our previous hypothesis that the in vivo intraepithelial IgG deposits in primary SS patients are due, at least in part, to cell surface-bound immune complexes.