Rheumatoid synovitis: complement and immune complexes

Area of Science:

• Immunology
• Rheumatology
• Molecular Biology

Background:

• Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by joint inflammation.
• The role of the complement system in RA pathogenesis is not fully understood.
• Immune complexes are implicated in the inflammatory processes of RA.

Purpose of the Study:

• To investigate the pattern of complement component utilization in the joints of RA patients.
• To correlate complement levels with clinical and radiological features of RA.
• To elucidate the role of complement activation in rheumatoid joint inflammation.

Main Methods:

• Immunofluorescence studies of synovial fluid (SF) leukocytes.
• Analysis of immunoglobulin and complement component inclusions within SF cells.
• Assessment of clinical, radiological, and pathological features in RA patients.
• Evaluation of systemic complement levels.

Main Results:

• Complement utilization in RA joints suggests activation by immune complexes.
• Intracytoplasmic inclusions of immunoglobulins and complement were found in SF leukocytes.
• Low SF complement levels were associated with unremitting RA, nodules, gold treatment, and more severe joint damage (radiological and pathological).
• Systemic hypocomplementemia indicated active RA with severe joint involvement and vasculitis.

Conclusions:

• Rheumatoid joint inflammation is mediated by the immunologic activation of the complement system.
• Complement activation via immune complexes plays a significant role in RA pathogenesis.
• Complement levels can serve as a marker for disease severity and activity in RA.