Comparison of three techniques for the detection of antibodies to double-stranded DNA: immunofluorescence on Trypanosoma gambiense, immunofluorescence on Crithidia luciliae and radioimmunoassay using the Farr technique.

Three techniques for the detection of antibodies against double-stranded DNA were compared: two immunofluorescent (IF) techniques using either Trypanosoma gambiense or Crithidia luciliae as antigen and a radioimmunoassay (RIA) based on the Farr technique. The IF on T. gambiense or C. luciliae gives very similar results but the reaction on C. luciliae is easier to read and to interpret. The use of C. luciliae permits the swift elimination of the two main causes of errors: antibodies against the nucleus of Trypanosomidae and antibodies reacting with the base of the flagella. The RIA appears as a very sensitive test since six sera gave a positive reaction with the RIA and a negative reaction with the IF on C. luciliae. However, the RIA gives in nine cases false positive reactions and in four cases false negative results. Those last four sera contained specific antibodies with low avidity for double-stranded DNA.