Epidermal nuclear IgG deposition in normal skin: characterization by anti-ribonucleoprotein IgG-Fab fragments

Epidermal nuclear IgG deposition in clinically normal skin may occur in patients with scleroderma or scleroderma-like features. In order to evaluate the mechanisms of the fixation, Fab fragments of anti-RNP IgG antibodies, obtained after papain digestion, were incubated for increasing times with various substrates: human skin, human mononuclear cells, cultured human fibroblasts and rabbit lip. Our results showed that anit-RNP IgG-Fab fragments could penetrate most of the living cells of human skin and rabbit lip and, to a lesser degree, mononuclear cells and poorly cultured fibroblasts. No ability to fix was found either with anti-RNP IgG-Fe fragments or with anti-nDNA/DNP IgG-Fab. It was concluded that anti-RNP IgG could penetrate viable epidermal and non-epidermal cells and that surface Fe receptors must play a minor role in the cellular penetration of antibodies.