A new serologic marker in ankylosing spondylitis.

Sera of patients with ankylosing spondylitis (AS) were screened for the presence of antibodies by indirect immunofluorescence staining of polytene chromosomes of Drosophila melanogaster. Thirty-nine percent of the sera tested contained antibodies which selectively reacted with an antigen(s) present at the chromosomal locus 93D after heat shock treatment. This indicates a novel antibody specificity in a subgroup of AS patients and may provide a new aid in the diagnosis of AS.