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Plasma C3 and C4 concentrations in management of glomerulonephritis
Insights
Complement C3 and C4 levels in nephritis patients provide key diagnostic insights. Lupus nephritis shows correlated C3/C4 dips, while acute nephritis and M.C.G.N. indicate bypass pathway activation.
Area of Science:
- Nephrology
- Immunology
- Clinical Chemistry
Background:
- Glomerulonephritis encompasses several kidney diseases characterized by inflammation of the glomeruli.
- Hypocomplementemia, a state of reduced complement levels, is often associated with specific nephritis types.
- Serial complement profiling aids in understanding disease activity and prognosis.
Purpose of the Study:
- To assess the clinical utility of measuring plasma C3 and C4 concentrations in patients with various forms of glomerulonephritis.
- To differentiate between nephritis subtypes based on complement profiles.
- To investigate complement activation pathways in lupus nephritis, acute glomerulonephritis, and mesangiocapillary glomerulonephritis (M.C.G.N.).
Main Methods:
- Plasma C3 and C4 concentrations were measured using commercially available immunodiffusion plates.
- A total of 303 samples were analyzed from 128 patients with lupus nephritis, M.C.G.N., and acute glomerulonephritis.
- Complement levels were correlated with clinical diagnoses and disease characteristics.
Main Results:
- In lupus nephritis, C3 and C4 generally correlated, with C4 more frequently and profoundly depressed than C3.
- Acute glomerulonephritis and M.C.G.N. often showed C3 concentrations below 20% of normal, suggesting bypass pathway activation, while C4 remained normal.
- C3 levels normalized within 8–12 weeks in acute glomerulonephritis but not M.C.G.N. M.C.G.N. with intramembranous deposits showed persistently low C3.
Conclusions:
- Plasma C3 and C4 measurements offer clinically valuable information for diagnosing and monitoring glomerulonephritis.
- Distinct complement profiles help differentiate between lupus nephritis, acute glomerulonephritis, and M.C.G.N.
- Complement activation via the bypass pathway is implicated in acute glomerulonephritis and M.C.G.N.
Abstract:
As part of a larger study of serial complement profiles in glomerulonephritis plasma C3 and C4 concentrations were measured using commercially available immunodiffusion plates. A total of 303 samples were obtained from 128 patients suffering from forms of nephritis associated with hypocomplementaemia-namely, lupus nephritis, mesangiocapillary glomerulonephritis (M.C.G.N.), and acute glomerulonephritis.These simple measurements of C3 and C4 gave clinically useful information. In lupus nephritis C3 and C4 generally correlated and C4 concentrations were more often and more profoundly depressed than C3 concentrations. Neither C3 nor C4 concentrations alone correlated well with the antinuclear factor titre.In both acute glomerulonephritis and M.C.G.N. the C3 concentrations were frequently lower than 20% of normal (which was never the case in patients with lupus), while the C4 concentration was usually normal and was almost never depressed in the absence of C3 depression. This suggests activation of complement at the C3 level by the "bypass" pathway in acute nephritis as well as in M.C.G.N., though both may be operating in some patients. In acute glomerulonephritis but not in M.C.G.N. C3 concentrations returned to normal within eight to 12 weeks.The two varieties of M.C.G.N. identified by the site of the deposits in the capillary glomerular walls differed in their C3 levels. In 10 patients with intramembranous dense linear deposits the C3 was always low over very long periods of time, rising in three out of four patients only after transplantation and immunosuppression. Other patients with M.C.G.N., in contrast, often showed normal C3 concentrations. Concentrations of C4 did not differ in either group, being normal in 80% of samples from all types.