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Proposed mechanism of the inflammatory attacks in familial Mediterranean fever
Y Matzner1, S K Ayesh, D Hochner-Celniker
1Hematology Unit, Hadassah University Hospital Mount Scopus, Jerusalem, Israel.
Abstract:
Peritoneal and synovial fluids of patients with familial Mediterranean fever lack a protein that inhibits neutrophil chemotaxis by antagonizing the complement-derived inflammatory mediator C5a. The C5a inhibitor activity was studied with the use of a C5a binding assay where peritoneal fluids were tested for their ability to inhibit recombinant C5a binding to dibutyryl cyclic adenosine monophosphate-induced U937 cells. In contrast to normal peritoneal fluids, those from patients with familial Mediterranean fever contained less than 1% C5a inhibitor activity. Gel filtration and ion exchange chromatography of peritoneal fluids from those patients did not yield any fraction that inhibited C5a binding. We suggest that the serosal tissue of patients with familial Mediterranean fever is devoid of C5a inhibitor activity and that this deficiency may explain in part the local inflammatory episodes characteristic of this disease.
Insights
Patients with familial Mediterranean fever lack a C5a inhibitor protein in their bodily fluids. This deficiency in C5a inhibitor activity may contribute to the characteristic inflammatory episodes of this genetic disorder.
Area of Science:
- Immunology
- Genetics
- Rheumatology
Background:
- Familial Mediterranean fever (FMF) is a genetic autoinflammatory disease characterized by recurrent episodes of fever and inflammation.
- Neutrophil chemotaxis, a key process in inflammation, is regulated by complement-derived mediators like C5a.
- A deficiency in inhibitors of inflammatory mediators could underlie the pathogenesis of FMF.
Purpose of the Study:
- To investigate the presence and activity of a C5a inhibitor in the peritoneal and synovial fluids of FMF patients.
- To determine if the absence of this inhibitor correlates with the inflammatory manifestations of FMF.
Main Methods:
- C5a binding assays were performed using peritoneal fluids from FMF patients and healthy controls.
- U937 cells stimulated with dibutyryl cyclic adenosine monophosphate were used as target cells for C5a.
- Chromatographic techniques, including gel filtration and ion exchange chromatography, were employed to isolate and characterize the C5a inhibitor.
Main Results:
- Peritoneal and synovial fluids from FMF patients exhibited significantly reduced C5a inhibitor activity (less than 1%) compared to normal fluids.
- No fractions capable of inhibiting C5a binding were isolated from the fluids of FMF patients using chromatographic methods.
- These findings suggest a systemic deficiency of the C5a inhibitor in FMF.
Conclusions:
- The serosal tissues of FMF patients appear to be devoid of C5a inhibitor activity.
- This deficiency in C5a inhibitor activity is a potential contributing factor to the localized inflammatory episodes observed in familial Mediterranean fever.
- Further research is warranted to elucidate the precise role of C5a inhibition in FMF pathogenesis.