Screening test for rheumatic diseases: a combined enzyme immunoassay of rheumatoid factors and antibodies to DNA and extractable nuclear antigens

Anti-idiotype antibodies in immune regulation of anca associated vasculitis

BACKGROUND

Anti-idiotype antibodies (anti-ids) have a potential role in the immunomodulation of various autoimmune disorders. The immunoregulatory role of anti-idiotypic antibodies in ANCA-associated vasculitis needs to be studied. This study was conducted in clinically and histopathologically diagnosed ANCA-associated vasculitis (AAV) patients.

METHODS

Anti-ids were tested in 100 AAV patients of which 80 had anti-MPO and 20 had anti-PR3 antibodies at various stages of disease over a period of 2-3 years. The disease activity was estimated by the Birmingham vasculitis activity score (BVAS). The affinity-purified ANCA F(ab')2 fragments were prepared using three each of anti-MPO and anti-PR3 high titer sera and were used as idiotype coats for anti-idiotype antibody detection by ELISA. Positivity was confirmed by fluid phase inhibition ELISA.

RESULTS

Patients who went into remission showed 53.8% anti-ids to anti-MPO and 52.9% to anti-PR3 with low BVAS values (0-8), whereas in patients with active disease, only 12.5% had anti-ids to anti-MPO and 10% had anti-ids to anti-PR3 with comparatively high BVAS (18-32), while five cases who had relapse (BVAS 18-20) did not have anti-ids to anti-MPO or anti-PR3. An inverse correlation was noted between ANCA and anti-ids (r = -0.901).

CONCLUSIONS

High prevalence of anti-ids in remission cases and low prevalence in active cases with absence of anti-ids in relapse cases as well as an inverse correlation of ANCA and anti-ids indicate its beneficial effect on the disease process, thus suggesting the dynamic role of anti-idiotype networks in the immunoregulation of AAV.

New methods for detection of anti-nuclear antibodies

Many different autoantibodies which react with a variety of different nuclear and cytoplasmic antigens have been described. Detection of some these antibodies has been shown to be clinically useful in a number of different autoimmune diseases. For many years, the detection of most of the clinically relevant antibodies was done with by immunofluorescence on tissue substrates and human cultured cell lines. Within the past few years, a number of technical advances has now made it possible to convert to enzyme immunoassay. The paper reviews the clinically relevant antibodies and discusses the variety of new methods which are now available for ANA detection in diagnostic laboratories.

Antigen association of total HEp-2 cell extract in the screening of autoimmune diseases by western blot

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.

Immunoblot assay for detection of autoantibodies in autoimmune disease

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.