Complement fixing antibodies to DS-DNA in systemic lupus erythematosus: a study using the immunofluorescent Crithidia luciliae method.

Crithidia luciliae, a hemoflagellate, was used in an immunofluorescent procedure to assay for antibodies to ds-DNA and their capacity to fix complement. Positive reactions with this method were limited to systemic lupus erythematosus patients, and sensitivity was comparable to the DNA binding assay. Complement fixing activity of antibodies to ds-DNA in 45 sera was determined using kinetoplast ds-DNA of Crithidia luciliae and an antiserum to C3. Complement fixing antibodies to ds-DNA were found in nearly all patients with documented active renal involvement and absent in nearly all patients with no, or inactive renal involvement.