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

Abstract

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.

Clinicopathological evaluation ofin vivoepidermal nuclear fluorescence

“…The finding of autoantibodies other than anti‐RNP is consistent with the concept of epitope spreading in systemic autoimmunity 20 . Anti‐SSA/Ro and anti‐SSB/La antibodies may participate in the pathogenesis of photosensitive skin lesions, 21–23 and IgG anti‐SSA/Ro may be found at epidermal surfaces of primary Sjögren’s syndrome 24 …”

“…20 Anti-SSA ⁄ Ro and anti-SSB ⁄ La antibodies may participate in the pathogenesis of photosensitive skin lesions, [21][22][23] and IgG anti-SSA ⁄ Ro may be found at epidermal surfaces of primary Sjögren's syndrome. 24 Velthuis et al 3 suggested in vivo ANA for the diagnosis of CTDs. They found a positive predictive value (PPV) of 88% whereas we found a PPV of around 75%.…”