Failure to Demonstrate Any Interaction Between Polyclonal Rheumatoid Factors and IgG Antinuclear Antibodies or Other IgG Autoantibodies

The autoantibody profile results from 750 randomly selected patients with rheumatoid factor (RF) and/or antinuclear antibody (ANA) positive tests were retrospectively analysed in order to discover if there was any evidence to show that the presence of polyclonal rheumatoid factors affects the incidence and titre of IgG-ANA in these patients. The incidence of IgG-ANA in the RF-positive group (34.4%) was significantly greater than that found in the RF-negative groups (19.6%) (P < 0.001), and there was no significant difference between the mean IgG-ANA titres of the two groups (P = 0.987). The possibility that the presence of IgM-RF in serum might be responsible for the inhibition of IgG-ANA was examined by treating the sera of selected patients who were RF-positive but IgG-ANA-negative with the dissociating agent D-penicillamine (DP). After treatment, IgG-ANA could not be detected in any of the sera. Similar studies were carried out to ascertain if there was a masking effect by RF on two other IgG autoantibodies, anti-keratin antibody (AKA) and gastric parietal cell antibody (GPCA). There was no evidence from these studies that the presence of RF affects the incidence of either AKA or GPCA. We conclude from these results that the presence of RF is not a significant factor controlling the incidence of either IgG-ANA or other IgG autoantibodies and that the routine treatment of RF-containing serum with a dissociating agent before testing for autoantibodies would be unnecessary.