Detection of anti-neutrophil cytoplasmic antibodies in dogs with immune-mediated inflammatory diseases

Anti-neutrophil cytoplasmic antibody (ANCA) is a type of autoantibody against neutrophil cytoplasm. In veterinary medicine, few studies have reported the detection of ANCA in dogs, and most of these studies were performed in dogs with inflammatory bowel disease (IBD). The aim of this study was to evaluate whether ANCA is detected in dogs with immune-mediated inflammatory diseases (IMIDs) other than IBD. Serum samples were collected before treatment initiation from 40 client-owned dogs with various diseases and 22 healthy beagle dogs; the dogs were classified into two groups: IMID group (n = 16) and control group (n = 46). ANCA was detected using the indirect fluorescent antibody test. Of the 16 dogs in the IMID group, 13 (81.3%) tested positive for ANCA. In contrast, of the 46 dogs in the control group, 13 (28.03%) tested positive for ANCA. Moreover, a significant association between ANCA positivity and IMIDs was identified in the IMID group than in the control group (P = 0.0003). In the control group, however, dogs with bacterial infection showed a relatively high rate of ANCA positivity. Therefore, ANCA positivity was observed in dogs with both IMIDs and bacterial infection. This suggested that ANCA positivity is associated with diseases accompanied by neutrophil activation and infiltration.