Immunofluorescence staining using Crithidia luciliae substrate detects which autoantibody?

Immunofluorescence staining using Crithidia luciliae substrate detects which autoantibody?

• A. Anti-dsDNA
• B. Anti-Smith
• C. Anti-RNP
• D. Anti-centromere

Answer: (A)

Crithidia luciliae substrate immunofluorescence is designed to detect antibodies against double-stranded DNA. The Crithidia organism has a kinetoplast that contains abundant dsDNA with minimal protein, so anti-dsDNA antibodies in a patient’s serum bind to this substrate. When a fluorescent secondary antibody is added, you see bright staining of the kinetoplast, a pattern highly specific for anti-dsDNA antibodies and thus supportive of systemic lupus erythematosus. Antibodies against Smith antigen, RNP, or centromere target proteins or RNA-associated complexes not present in the Crithidia kinetoplast, so they don’t produce this distinctive kinetoplast fluorescence. Therefore, the best answer is anti-dsDNA.

Crithidia luciliae substrate immunofluorescence is designed to detect antibodies against double-stranded DNA. The Crithidia organism has a kinetoplast that contains abundant dsDNA with minimal protein, so anti-dsDNA antibodies in a patient’s serum bind to this substrate. When a fluorescent secondary antibody is added, you see bright staining of the kinetoplast, a pattern highly specific for anti-dsDNA antibodies and thus supportive of systemic lupus erythematosus. Antibodies against Smith antigen, RNP, or centromere target proteins or RNA-associated complexes not present in the Crithidia kinetoplast, so they don’t produce this distinctive kinetoplast fluorescence. Therefore, the best answer is anti-dsDNA.