Technical Aspects of ANA Determination

With the introduction of several new techniques, the study of antinuclear antibodies (ANA) is becoming an exciting topic in immunological technology. For a long time it has been evident that the immunofluorescence technique (IFT) on tissue sections to detect ANA next to the advantage of being simple, has the severe drawback that a variety of nuclear antigens are treated in an undifferentiated way. This is demonstrated by the variation in reaction pattern of patients’ sera with nuclei from different sources and by the multiple staining patterns that can be observed using different sera (for a review see ref. 1). These intriguing findings led to an effort to separate the various nuclear antigens. The first antigen to be thoroughly studied was DNA. Protein antigens proved to be much more difficult to identify and it is only recently that progress in this field has been boosted by the development of monoclonal antibodies to nuclear antigens and the application of new techniques of which western blotting of nuclear antigens is the most prominent (2-5). As a result ANA research is flourishing as never before. LESSONS FROM THE DNA/ANTI-DNA SYSTEM In this meeting a lot has been said about these new techniques and interesting data have been presented regarding the characteristics of a number of nuclear antigens and the clinical implications of antibodies against them. Nevertheless I feel that some cautious remarks have to be made in view of these developments. The caution is induced by the work on antibodies to DNA. As stated before, DNA was the first antigen to be thoroughly studied. The main reason for that probably is the relative ease with which DNA can be obtained in a pure form. When in 1970 we started to work on anti-DNA, people around us tried to discourage us with the remark that everything had already been done. How wrong they were. Fourteen years later we have learned a lot more about the system. We have gathered some answers, but a lot of questions are still left. Let me give some examples. Comparison of various anti-dsDNA assays For the detection of anti-DNA a number of different assays has been developed. We did work on three particular assays, being the Farr assay (6), the Crithidia luciliae (CL) assay (7) and the PEG-assay (8).