Characterisation of autoantibodies to neutrophil granule constituents among patients with reactive arthritis, rheumatoid arthritis, and ulcerative colitis

Objective-To study the frequency and distribution of antineutrophil cytopla smic autoantibodies (ANCA) among patients with reactive arthritis (ReA), rh eumatoid arthritis (RA), and ulcerative colitis (UC) using different immuno logical methods. Methods-Fifty serum samples from patients with reactive arthritis (26 with acute disease and 24 with chronic disease-that is disease of more than one year) were analysed for ANCA with indirect immuno-fluorescence, enzyme link ed immuno-sorbent assay (ELISA) with six different neutrophil granule prote ins as antigens, and immunoblotting on whole neutrophil extract and extract s of azurophil and specific granules. Thirty serum samples from patients wi th RA and UC served as controls in ELISA and indirect immunofluorescence. Results-Sixteen per cent of patients with ReA were positive in immunofluore scence compared with 30% of patients with RA, and 70% of patients with UC. Thirty two per cent of patients with ReA were positive in ELISA. Antibodies directed against lactoferrin occurred in 20%, antibodies against bacterici dal permeability increasing protein (BPI), elastase, cathepsin G, myelopero xidase, and proteinase 3 were found in 8%, 2%, 2%, 8%, and 6%, respectively . Overall, 50% of RA sera and 53% of UC sera were positive in one or more E LISA assays, the corresponding figures for antibodies against individual an tigens were for RA 7%, 3%, 0%, 13%, 47%, 17% and for UC 13%, 20%, 0%, 23%, 10%, and 17%. In immunoblotting, bands corresponding to lactoferrin and BPI were recognised in 44% and 22% of ReA sera. Conclusion-Antibodies against neutrophil granule antigens are often found i n patients with ReA, primarily among those with chronic disease. The differ ent methods detect various subsets of antibodies, with immunoblotting being the most and immunofluorescence the least sensitive.