Narrow-band UVB-induced externalization of selected nuclear antigens in keratinocytes: implications for lupus erythematosus pathogenesis.

The aim of this study was to analyze whether sera obtained from patients with lupus erythematosus (LE) react with membrane structures found on keratinocytes irradiated with narrow-band ultraviolet B (NB-UVB). We applied atomic force microscopy (AFM) to visualize cell surface structures expressing nuclear antigens upon apoptosis following NB-UVB irradiation. Immortalized human keratinocytes (HaCaT) were cultured under standard conditions, irradiated with 800 mJ cm(-2) NB-UVB light and imaged by AFM mounted on an inverted optical microscope. It was observed that NB-UVB irradiation provoked significant alterations of the keratinocyte morphology and led to the membrane expression of antigens recognized by anti-La and anti-Ro 60 kDa sera but not by antidouble-strand DNA sera. The presence of La and Ro 60 kDa antigens on keratinocyte surfaces after NB-UVB irradiation was limited mainly to the small bleb-like protrusions found on the keratinocytes by AFM. A closer investigation by AFM also revealed that some structures positively stained with anti-Ro 60 kDa serum were also located submembranously. We hypothesize that the externalization of some nuclear antigens because of NB-UVB exposure might be responsible for exacerbation of skin symptoms in patients suffering from LE.