Complement‐fixing hidden rheumatoid factor in juvenile rheumatoid arthritis

Abstract

Fifteen to twenty percent of patients with juvenile rheumatoid arthritis (JRA) have positive latex fixation tests (LFT), whereas approximately 46% have previously been demonstrated to have hidden rheumatoid factors (RF), i.e., 19s IgM RF which can be detected by the LFT after acid separation of the IgM-containing fraction from serum. In this study, hidden RF were found in 59% of patients with seronegative JRA by use of a complementdependent hemolytic assay. The median titer of JRA patients was l :42, and in healthy and disease controls it was 1 :7. The difference was significant at P < 0.001. When data from patients with active disease were analyzed separately, the median titer for polyarticular JRA was l :97 and for pauciarticular JRA, 1 :91. The differences due to active disease were significant at P < 0.001 and P < 0.005, respectively.The results demonstrate that the hemolytic assay is more sensitive than the LFT in determining the presence of hidden RF, and activity of disease correlates well with high hemolytic R F titers.

19S IgM Rheumatoid Factor-7S IgG Rheumatoid Factor Immune Complexes Isolated in Sera of Patients with Juvenile Rheumatoid Arthritis

“…(7)(8)(9). Previous studies had demonstrated the association of active disease in JRA patients with polyarticular and pauciarticular onset who had 19S IgM RF or hidden 19S IgM RF circulating in their sera (5,6). The new findings of the 19S IgM RF association with IC formation in JRA initiated the present study.…”

“…The presence of elevated IC as detected by the C1q binding assay or the Clq solid-phase assay, also, correlated with the presence of 19S IgM RF (2,3) and hidden 19S IgM RF (3) [i.e. 19S IgM RF which can be detected in the IgM-containing fraction by the hemolytic assay after separation of serum by acidgel filtration (5,6)]. IC presence has also correlated with active disease, demonstrating a connection with a more advanced stage of disease and possible prognostic parameter (3,4).…”

“…The assay was performed on the IgM-containing fractions from a Sephadex G-200 column as previously described in detail (5,6).…”

Activation of the classical pathway of complement by rheumatoid factors

“…IgG-RF seems to play no significant role: it neither augmented nor diminished complement activation by IgM-RF. In contrast, considerable inhibition of complement activation by RF has been described using the hemolytic assay (8, 25).…”

Complement‐fixing hidden rheumatoid factor in children with benign rheumatoid nodules

“…The possibility that hidden R F might be present in these patients was entertained because of recent studies in our laboratory that revealed the presence of hidden R F in high titer when a hemolytic assay was performed on separated IgM fractions of patients with seronegative JRA (21). Hidden R F is 19s IgM R F that probably has been complexed in the peripheral blood with 7s IgG and therefore is not detected by standard laboratory tests.…”