Abstract: Objective To study the action and mechanism of staphylococcal exfoliative toxin A(E-TA)on pemphigus foliaceus antigen(PFA)and pemphigus vulgaris antigen(PVA)expressed on cultured human keratinocytes.Methods Stratified human keratinocytes were incubated with ETA and then stained with sera from patients with pemphigus foliaceus or pemphigus vulgaris as the first antibodies and FITC-la-beled sheep anti-human IgG as the second antibody.Total protein was harvested from the cells pretreated with ETA and run on SDS-PAGE for Western blot with the same antibodies.Simultaneously,supernatants of the keratinocytes before and after ETA treatment were collected for detection of the levels of IL-1α,IL-6 with ELISA kits.The caseinolytic activities of the supernatants were tested by spectrometry in which casein was used as a non-specific substrate.Results Down-expression of PFA was shown after ETA treatment while no change of PVA expression was found.The high intensity and continuous linear appearance of fluo-rescent staining before ETA treatment became weak and discontinuous after ETA treatment,which were re-covered gradually in 24 hours.The degradation of proteins recognized by PF sera after ETV treatment was revealed by Western blot.The decreasing tendency of IL-1α concentration was found in the supernatants of cell culture after ETA treatment,but IL-6 level was too low to be detected.Increased caseinolytic activities were found in the supernatants,and declined 36 hours after ETA treatment.Conclusions ETA acts on PFA expressed on keratinocytes in vitro,which is reversible along with withdrawal of ETA.The mechanism of E-TA act on PFA may be related to proteolytic action instead of promoting cytokine secretion.

Key words: Pemphigus, Exfoliative toxins, Keratinocytes, Interleukines, Peptide peptidohydro-lases