IgM and IgA rheumatoid factors in canine polyarthritis

Abstract

IgM and IgA rheumatoid factor (RF) were detected by ELISA using a purified dog IgG as antigen in normal controls ( N = 84), dogs with unclassified polyarthritis ( N = 95), dogs with rheumatoid arthritis (RA) ( N = 22), dogs with systemic lupus erythematosus (SLE) ( N = 35), dogs with leishmaniasis or heart worm disease ( N = 20) and dogs with pyometra ( N = 16). Frequency and titre of IgM and IgA RF are low and comparable ( P < 0.05) in dogs with unclassified polyarthritis or RA: respectively 24.2% and 27.3% for IgM RF and 21.0% and 18.2% for IgA RF; the mean titre being respectively 0.781 ± 0.581 and 0.649 ± 0.365 for IgM RF, and 0.774 ± 1.331 and 0.740 ± 1.169 for IgA RF. The frequencies of IgM and IgA RF are a little higher in dogs with SLE (IgM RF: 37.1%, IgA RF: 25.7%) and higher in dogs with leishmaniasis or heart worm disease (45.0% and 30.0%), especially in dogs with pyometra (68.7% and 37.5%). So, although dogs can produce IgM and IgA RF, these auto-antibodies are uncommon in dogs with RA. Furthermore, when RF are present their titre is much lower than in human RA.