BPI-ANCA is found in reactive arthritis caused by Yersinia and Salmonella infection and recognise exclusively the C-terminal part of the BPI molecule

Objective: To examine the prevalence, binding sites and functional interact ions of antineutrophil cytoplasmic autoantibodies (ANCA) against the bacter icidal/permeability increasing protein (BPI) in reactive arthritis (ReA). Methods: Sera were analysed for the occurrence of ANCA by indirect immunofl uorescence microscopy (IIF) and ELISA. Binding sites were determined using BPI, lipopolysaccharid binding protein (LBP), and fusion proteins of both p roteins in ELISA. In addition, the effect of antibodies on the antibiotic a ctivity of BPI was examined. Results: BPI-ANCA was found in patients with Yersinia- and Salmonella-trigg ered ReA and directed against the C-terminal portion of BPI. Goat anti BPI antibodies recognising this part inhibited the antibiotic activity of BPI i n vitro. Conclusion: BPI-ANCA was associated with ReA triggered by Salmonella and Ye rsinia infection. Directed against the C-terminal part of BPI, it can poten tially inhibit its antibiotic activity and might be useful to identify pati ents with infectious bowel disease prone to extraintestinal sequelae.