Antigenic properties of a DNA-preparation from calf thymus used for the demonstration of anti-DNA.

It was attempted to evaluate passive haemagglutination of antigen coated, tanned erythrocytes as a test by which to demonstrate anti-DNA in systemic lupus erythematosus. The antigens was prepared using a minimum of procedures in order to produce a native preparation. The resulting material had most of the criteria applying to native DNA, but the protein content was about 9%. It contained a thymocyte specific component, but no demonstrable trace of bovine species antigen. The reactions between the antigen and an anti-DNA serum from a patient with suspected SLE were inhibited by DNA and DNA-histone, but not appreciably by ENA, RNA or desoxyribonucleosides. Passive haemagglutination reactions against the antigen were positively correlated to a homogeneous immunofluorescence nuclear pattern and negatively correlated to a speckled pattern. Passive haemagglutination titres against ENA and DNA antigen were not correlated. Seventy-three per cent of randomly selected sera gave either purely DNase sensitive reactions (19%) or reactions of combined sensitivity to DNase and other enzymes. Twenty-eight out of 53 sera reacting in the passive haemagglutination test reacted also in the immunofluorescence test against Chrithidia luciliae kinetoplasts. The latter reactions were DNase sensitive. It applies to both tests that DNase sensitive, but RNase resistant, reactions were well correlated, irrespective of their sensitivity to trypsin while DNase resistant or DNase and RNase sensitive reactions were not correlated. The passive haemagglutination test using a native but relatively crude DNA-preparation coated on tanned sheep erythrocytes supplemented by specificity tests with DNase and RNase treated antigen gives about the same information as the indirect immunofluorescence test against Chrithidia luciliae kinetoplasts. Furthermore, the results show that patients' sera reacting with a homogeneous nuclear pattern in the indirect immunofluorescence test may contain not only anti-DNA and anti-nucleohistone antibodies, but also antibodies to a number of non-histone chromatin associated proteins some of which contain RNA.