Anti-lactoferrin antibodies and other types of anti-neutrophil cytoplasmicantibodies (ANCA) in reactive arthritis and ankylosing spondylitis

Fifty-five serum samples from patients with reactive arthritis (ReA), 40 fr om patients with ankylosing spondylitis (AS) and three from patients with c hronic sacroiliac joint arthritis were analysed for the presence of ANCA of IgG class by means of enzyme immunosorbent assay using lactoferrin (Lf), m yeloperoxidase (MPO) and antigen extracted from azurophil granules ('alpha- antigen') containing proteinase 3 (PR3) as substrate. IgG-ANCA were found i n 31 (56%) patients with ReA. Twenty-three (42%) had anti-if antibodies, ni ne (16%) had anti-MPO and eight (15%) had anti-alpha-antigen antibodies, no ne of which reacted with PR3. Only six ( 14%) AS or sacroiliac joint arthri tis patients had ANCA (P<0.001). Three (7%) had anti-if, two (5%) anti-MPO and two (5%) anti-alpha-antigen antibodies. Yersinia and Salmonella bacteri a were separated by SDS-PAGE and blots were incubated with serum from rabbi ts immunized with human if. The hyperimmune serum recognized a band of 78 k D from both bacteria which was not seen when preimmune serum was used. The reaction to the 78-kD antigen could be completely inhibited when anti-if an tibodies were absorbed on if coupled to cyanogen bromide-activated Sepharos e, possibly indicating cross-reacting epitopes in if and enterobacterial an tigen.