ENHANCED MEMBRANE EXPRESSION OF THE 52 KDA RO(SS-A) AND LA(SS-B) ANTIGENS BY HUMAN KERATINOCYTES INDUCED BY TNF-ALPHA

Objective-To investigate the membrane expression of the 52 kDa Ro(SS-A ) and La(SS-B) antigens in human keratinocytes under the influence of an important mediator of inflammation, TNF alpha. Methods-Keratinocyte s, isolated from human skins obtained at circumcision and identified u sing monoclonal antibodies, were treated with tumour necrosis factor a lpha (TNF alpha) and incubated with antibodies to 52 kDa Ro(SS-A) isol ated and purified from patients with systemic lupus erythematosus or S jogren's syndrome, with mouse monoclonal antibody to La(SS-B), and (as controls) with sera from normal healthy blood donors and a mouse mono clonal antibody to U1RNP 68 kDa. Membrane expression of the 52 kDa Ro( SS-A) and La(SS-B) antigens was detected using cyto enzyme linked immu nosorbent assays (ELISAs), laser scanning microscopy, and indirect imm unofluorescence. Results-After the incubation with TNF alpha, cyto ELI SA revealed a significantly increased membrane binding of 52 kDa Ro(SS -A) antibodies, with a maximum after two hours, followed by enhanced 5 2 kDa Ro(SS-A) expression during the subsequent 24 hours. The La(SS-B) antigen was expressed rapidly after TNF alpha treatment (within one h our), with a fast decrease to the preincubation value within three hou rs. Indirect immunofluorescence with fixed normal human keratinocytes confirmed increased 52 kDa Ro(SS-A) and La(SS-B) antigen expression af ter the incubation with TNF alpha. Conclusions-TNF alpha mediates 52 k Da Ro(SS-A) and La(SS-B) autoantigen surface expression on human kerat inocytes, and may be an important factor both in antibody induction an d in the initiation of immunopathogenic processes which occur after an tibody binding in autoimmune dermatitis.