TRANSFECTION AND OVEREXPRESSION OF THE HUMAN 60-KDA RO SS-A AUTOANTIGEN IN HEP-2 CELLS/

A full-length cDNA encoding human 60-kDa Ro/SS-A protein was transfect ed into and overexpressed in the human cell line HEp-2, with the aim o f developing an improved reagent for indirect immunofluorescence (IF) detection of anti-Ro autoantibodies. Stable transfectants were analyze d by IF using a panel of 20 precipitin-positive anti-Ro human sera. Tr ansfectants showed bright finely speckled nuclear and nucleolar staini ng. No surface membrane expression was detected despite marked overexp ression of 60-kDa Ro. All human anti-Ro sera reacted with the transfec tants with titers ranging from 1:320 to 1:40,960. The same sera tested on untransfected cells showed titers from negative (3 sera) to 1:160. These transfectants dramatically increase the sensitivity of IF testi ng (mean increase in titer of 41-fold) and allow detection of specific anti-Ro antibodies in samples negative or equivocal on untransfected cells. The staining patterns of antisera of other important specificit ies remained unaltered. In a study of sera from 22 patients with syste mic lupus erythematosus, anti-60-kDa Ro autoantibodies were detected i n all sera when tested on 60-kDa Ro-transfected HEp-2 cells; however, in 12 of 22 sera autoantibodies were undetectable by recombinant 60-kD a Ro ELISA. The 60-kDa Ro transfectants are a simple and sensitive met hod for detection of anti-Ro antibodies in patients with systemic rheu matic diseases. (C) 1994 Academic Press, Inc.