Screening tests for antinuclear antibodies (ANA): selective use of central nuclear antigens as a rational basis for screening by ELISA.

Rational, fully automated ELISA screening tests for ANA have become accessible for routine use. Full length, recombinant or purified naturally expressed antigens can be selected to deliver well defined screening tests, designed to detect ANAs of established clinical significance, while unknown specificities with no clear biological impact are omitted. By comparing results of ANA screening by immunofluorescence (IIF) on tissue section with HEp-2 cells, a correlation of 88% was revealed, while 86% of HEp-2-positive sera bound tissue sections. Eighty-nine percent of HEp-2 ANA-positive sera bound in ANA ELISA I. Seventy-five percent of ANAs detected in ELISA I also bound in ELISA II. These correlations were statistically significant. ANAs detected in ANA ELISA I were all detected upon retesting in both ANA screening ELISA systems, and also by antigen-specific ELISAs. Specific ANAs defined by ELISA, immunodiffusion or Crithidia tests were detected in both ANA ELISA tests. These data demonstrate that most ANAs detected by immunofluorescence tests contain a dominating repertoire of specificities covered by the ANA ELISA systems. The sensitivity of the different ELISA tests can easily be adjusted to internationally defined consensus levels, and screening for ANA using both ELISA systems detects expected ANA specificities in ongoing international quality assessment programs.

Linked production of antibodies to mammalian DNA and to human polyomavirus large T antigen: footprints of a common molecular and cellular process?

OBJECTIVE: To test whether the presence of antibodies to human polyomavirus large T antigen, a viral DNA-binding protein essential for productive polyomavirus replication, correlates with the presence of antibodies to single-stranded DNA (ssDNA), double-stranded DNA (dsDNA), or the autologous TATA-binding protein (TBP). METHODS: Sera from patients with various diagnosed or suspected autoimmune syndromes were analyzed for the presence of antibodies to T antigen, DNA, or TATA-binding protein, and correlations were determined. Rheumatoid factor (RF) was studied as a control antibody. RESULTS: A highly significant correlation between antibodies to T antigen and antibodies to ssDNA or TATA-binding protein, but not between anti-T antigen antibodies and RF, was found in all patient groups. Of all sera that were positive for antibodies to dsDNA, 62% were positive for antibodies to T antigen (P<0.03). CONCLUSION: A non-self DNA-binding protein such as human polyomavirus large T antigen may render DNA immunogenic upon binding to nucleosomes when expressed in vivo. This is indicated by the strong correlation between antibodies to T antigen and antibodies to DNA or TBP and is consistent with a hapten-carrier model. This model implies cognate antigen-selective interaction of T antigen-specific T helper cells and DNA-specific B cells or B cells specific for other components of nucleosomes, consistent with the results of previous experiments.