Fibroblast monolayers as substrates for the demonstration and analysis of anti-nuclear autoantibodies.

Monolayers of acetone-fixed cultured fibroblasts were compared with frozen tissue sections as substrates for the immunofluorescent demonstration of anti-nuclear autoantibodies (ANA) in 8 sera. Fibroblast monolayers gave more readily recognizable nuclear staining patterns and more intense staining reactions. Pretreatment of acetone-fixed monolayers with DNase, RNase, trypsin, 2M NaCl or 0.2 HCl before exposure to test sera, permitted analysis of the nature of the ANA-reactive nuclear antigens and unmasked "hidden" anti-nucleolar and possibly antinuclear matrix autoantibodies in 4 sera with homogeneous ANA reactivity. The observations suggest that autoantibodies to nucleoli may be commoner than hitherto reported and that fibroblast monolayers may prove to be a useful ancillary substrate for the diagnosis and analysis of ANA.