Rabbit antisera to enterobacteriaceae isolated from HLA-B27 positive patients with ankylosing spondylitis (AS) are lytic for the mononuclear cells of AS patients.

Vaccines prepared from Gram-negative bacteria isolated from the stools of HLA-B27 positive AS patients were used to immunize rabbits. Three of the sera obtained were lytic in vitro for the mononuclear cells of HLA-B27 positive AS patients. One of these sera discriminated between AS patients and healthy HLA-B27 positive individuals. Cytolysis was determined in an automated, non-radioactive assay based on the release of carboxyfluorescein diacetate and the incorporation of propidium iodide.