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Inherited deficiencies of complement in rheumatic diseases
1Department of Medicine, Division of Rheumatology, Emory University School of Medicine, Atlanta, Georgia, USA.
Insights
Inherited complement deficiencies, particularly in the early classical pathway, are linked to systemic lupus erythematosus. Assays measuring complement activation may help track disease activity and flares.
Area of Science:
- Immunology
- Genetics
Background:
- Inherited complement deficiencies are uncommon but more prevalent in systemic lupus erythematosus (SLE) patients.
- The complement system plays a crucial role in immune responses and maintaining self-tolerance.
Purpose of the Study:
- To review the fundamentals of complement activation and biology.
- To highlight recent findings on the association between complement deficiencies and SLE.
- To discuss the diagnostic potential of complement activation product assays in SLE.
Main Methods:
- Literature review of complement biology and SLE associations.
- Analysis of existing data on complement deficiencies and autoimmune disease.
- Evaluation of the utility of complement activation assays.
Main Results:
- Homozygous C1q deficiencies and C4A null allotypes show a strong association with SLE.
- Deficiencies in C2 and C3 are less consistently linked to autoimmune disease.
- A functional early classical complement pathway appears important for preventing SLE.
Conclusions:
- The hierarchy of associations suggests the early classical pathway's critical role in SLE prevention.
- Complement activation product assays may offer sensitive and specific markers for SLE disease activity and flares.
Abstract:
Inherited complement deficiencies are rare but occur with increased frequency in systemic lupus erythematosus. This selective review summarizes the fundamentals of complement activation and biology and focuses on recent findings. system lupus erythematosus is highly associated with homozygous C1q deficiencies and with C4A null allotypes, and homozygous C2 and C3 deficiencies are less uniformly associated with autoimmune disease. This hierarchy of disease associations suggests the importance of an intact early classic activation pathway in preventing systemic lupus erythematosus. Assays of complement activation products may have greater sensitivity and specificity for systemic lupus erythematosus disease activity and lupus flares.