The basic problem in serodiagnostics of autoantibodies concerns situations when at very high ANA titres we cannot estimate the specificity of an autoantibody or, what is even worse, the ANA pattern is partially or totally incompatible with specificities estimated by other immunoenzymatic methods. Solving this problem is the main goal of the presented work. Comparison of four methods of anti-dsDNA assessment gives us only 45% quantitative agreement. Sensitivity of tests used for anti-dsDNA and also ANA-IIF-Hep-2 test, to neutralization by dsDNA, ssDNA and RNA, showed significant lowering of anti-dsDNA antibody levels, up to negativity. Titration of doses of antigens needed for neutralization of used tests showed no differences in neutralizing doses between ds and ssDNA and only neutralizing doses for RNA were 10 times greater.
This unexpected result caused the need to assess specificity and avidity of antibodies eluted by the affinity method. Independently of the antigen used for elution, antibodies showed reactivity with two other antigens, for example: antibodies eluted from ssDNA bound to nitrocellulose also showed reactivity with dsDNA and cardiolipin, and generally they were antibodies of low avidity index.
To summarize, conformation and stability of dsDNA preparations (resulting from presence of denatured DNA fragment in dsDNA molecule) exclude the simple possibility of differentiation of separated antibody pools against DNA and makes (in cases of anti-dsDNA antibody assessment) affinity or avidity estimation necessary. Solving these problems will be possible (as we planned) by using synthetic DNA analogues such as polynucleosides.