Antibodies against macaque monoclonal immunoglobulin G in rheumatoid arthritis

The presence of rheumatoid factors (RF) in the serum of rheumatoid arthriti s (RA) patients is commonly evidenced by agglutination tests: the Waaler-Ro se assay, based on the use of human red blood cells (RBCs) coated with rabb it anti-RBC antibodies, and the latex test, which uses latex particles coat ed with denatured human immunoglobulin G (IgG). The aim of the present stud y was to characterize the RF able to agglutinate human RBCs coated with mac aque antihuman RBC IgG antibodies secreted from macaque-mouse heterohybrido mas (two from rhesus monkey and one from crab-eating macaque). Human RBCs c oated with macaque monoclonal antibodies (MacMoAbs) were used for agglutina tion tests and these were carried out in parallel with standard tests (Waal er-Rose and latex agglutination tests) on sera from 82 RA patients, 86 pati ents with other forms of inflammatory chronic arthritis and 47 healthy huma n subjects. MacMoAb-coated RBCs identified RF in the sera of 66% patients w ith RA. By contrast, the frequency of positive sera in other inflammatory d iseases was 5% and all 47 healthy controls were negative. Antimacaque IgG a ntibodies were found to be more specific for RF than standard tests, in the sera of patients with RA.