The first international standard for antibodies to double stranded DNA.

This paper announces the availability of the first international standard for anti-double-stranded DNA (anti-dsDNA). The material, coded Wo/80, was obtained after recalcification of plasma taken from a patient with systemic lupus erythematosus. Vials were filled with 500 microliters serum and freeze dried. The serum contains no other autoantibodies in measurable quantities. The vials should be stored at -20 degrees C. The standard should be used for establishing national, regional, or local standards. In eight laboratories satisfactory results with the immunofluorescence technique on Crithidia luciliae were obtained; the titres varied between 1/20 and 1/640 (mean 1/160). In seven laboratories the Farr assay, with the so called 'Amersham kit', was performed. At a dilution of 1:40 a mean binding percentage of about 50% was observed. After reconstitution with 500 microliters of distilled water, the vial contains 100 IU/500 microliters or 200 IU/ml. The standard can be obtained from the custodian of WHO: Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, PO Box 9190 1006 AD Amsterdam, The Netherlands.