Hidden 19S IgM rheumatoid factor in synovial fluid

Area of Science:

• Rheumatology
• Immunology
• Biochemistry

Background:

• Rheumatoid arthritis (RA) is an autoimmune disease characterized by joint inflammation.
• Rheumatoid factor (RF) is an autoantibody often found in RA patients.
• The presence and significance of hidden 19S IgM RF in synovial fluid require further investigation.

Purpose of the Study:

• To investigate the presence of hidden 19S IgM rheumatoid factor (RF) in synovial fluid (SF) from adult and juvenile rheumatoid arthritis (RA and JRA) patients.
• To determine if hidden 19S IgM RF is detectable in seronegative RA and JRA cases.

Main Methods:

• Synovial fluid samples from RA and JRA patients were processed.
• Incubation with hyaluronidase, dialysis against acetate buffers, centrifugation, and Sephadex G-200 column chromatography were employed.
• Complement-dependent hemolytic assay was used to detect RF activity.

Main Results:

• Hidden 19S IgM RF activity was demonstrated in the IgM-containing SF fraction of 5 seropositive patients (3 adult RA, 2 JRA).
• No hidden 19S IgM RF was found in seronegative adult RA patients.
• Hidden 19S IgM RF was detected in 4 of 7 seronegative JRA patients.

Conclusions:

• Hidden 19S IgM RF can be present in the synovial fluid of rheumatoid arthritis patients, including those initially seronegative.
• Juvenile rheumatoid arthritis patients, particularly seronegative cases, may harbor detectable hidden 19S IgM RF in their synovial fluid.
• These findings contribute to understanding the complex immunological profile in rheumatoid arthritis.