When detecting antinuclear antibodies (ANA) a similar indirect immunofluorescence (IIF) pattern may be produced by antibodies which correspond to different antigenic specificity or to diverse autoimmune disorders. To circumvent this problem, we used an immunoblotting against total antigen from HEp-2 cells (TA-HEp-2-C) which proved to be more specific and sensitive than IIF, since it detected up to 40 antigenic bands and an immunoblot pattern characteristic of each individual and unrelated to the fluorescence patterns of ANA. The analysis of immunoblot patterns is of great diagnostic value, since in patients with systemic lupus erythematosus (SLE) the antigenic zone is found between 21 and 48 kDa, whereas in other rheumatic diseases with or without positive ANA antibodies by IIF it is found between 14 and 21 kDa. Bands which appear after 50 kDa may or may not have pathological significance since they are present in most normal individuals. The use of reference sera allowed the identification in the extract of previously described antigens relevant to these diseases. Some patients showed bands which have yet to be reported and may be clinically significant on their own or in association with other autoantibodies. The long-term follow-up of these immunoblot patterns may prove to be of prognostic importance.

Sera from patients with autoimmune diseases and healthy individuals were comparatively analyzed by Western blot, using total extract from HEp‐2 cells as antigen. Bands between 14 and 20 kDa were present in 99% of patients with autoimmune diseases and symptomatic seronegative patients, in contrast to only 4% of healthy controls. No bands were detected in the remaining 96% of healthy controls. We propose these antigens as pathologically important for the diagnostic screening of patients with suspected autoimmune disease. © 1996 Wiley‐Liss, Inc.