Biological Significance of Nuclear Antigens' Expression on Cell Surface

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1) In order to understand the potential mechanisms of ultraviolet light B (UVB) on photosensitivity in lupus erythematosus ( LE), we designed immunopathologic in vitro and in vivo experiments to evaluate the effects of UV on the binding of anti-extractable nuclear antigent (ENA) antibodies to the surface of human keratinocytes. Short-term 2% paraformaldehyde fixation of suspensions of cultured human keratinocytes previously incubated with monospecific antiserum probes enabled the detection of ENA expression on the cell surface by flow cytometry analysis. In vitro FACS analysis revealed that ENA augmentation on the keratinocyte cell surface was UVB dose dependent, glycosilation dependent, and cell cycle independent. In vivo augmentation on the keratinocyte surface was also demonstrated in suction blister epidermal roof.2) Among PG reagents, PGJ2 could augment the binding of anti-ENA antibodies to cultured keratinocytes in serum-free medium. However, anti-Smantibody's binding was not ind … More uced by PGJ_2. Enhanced bindings of anti-RNP, anti-SS-A/Ro antibodies were demonstrated by the standard immunofluorescence technique and the FACS analysis using post-fixation methods. These binding were blocked by cyclohexamide.These results suggest that the inducers of heat shock protein or stress protein are triggers of development of skin manifestation of cutaneous LE.3) As a next step, the cytotoxic mechanisms of cutaneous LE were investigated. Monocytes from SLE or subacute cutaneous LE were co-cultured with keratinocytes treated with PGJ_2 or cells irradiated with UVB. Irrespective of the presence or the absence of complement source, the significant number of cultured keratinocytes was damaged under the influence of antiserum probes.These results indicate that the cytotoxic mechanisms such as antibody dependent cell-mediated cytotoxicity (ADCC) are involved in the pathogenesis of cutaneous LE.4) Expression of nuclear antigens on the cells of blood vessels was also investigated. UVB could induce anti-RNP antibody binding of cryostat sections of skin specimens. The bindings were observed on the endothelial cells of dermis. The specificity of this positive findings is now under careful in stigation. Less