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Serum complement components in Henoch-Schönlein purpura
Insights
Complement activation occurs in Henoch-Schönlein purpura (HSP), particularly the alternative pathway. Low properdin levels in acute HSP suggest this pathway is involved in the condition.
Area of Science:
- Immunology
- Nephrology
Background:
- Henoch-Schönlein purpura (HSP) is a systemic vasculitis.
- The role of the complement system in HSP pathogenesis is not fully understood.
Purpose of the Study:
- To investigate complement activation in patients with Henoch-Schönlein purpura.
- To determine which complement pathways are involved in acute and chronic HSP.
Main Methods:
- Serum levels of complement components (C1q, C4, C3, C5, factor B, properdin) and CH50 were measured.
- Patients with acute HSP and chronic nephritis following HSP were analyzed.
Main Results:
- In acute HSP, low CH50 (39%) and low properdin (30%) were observed, while C1q, C4, and C3 remained normal.
- In chronic nephritis post-HSP, complement components were generally normal, with occasional reductions in C4 and properdin.
- Low properdin levels in acute HSP indicate alternative pathway activation.
Conclusions:
- Complement activation is confirmed in Henoch-Schönlein purpura.
- The alternative complement pathway is likely activated in acute HSP.
- Complement abnormalities are less pronounced in chronic nephritis following HSP.
Abstract:
Serum levels of C1q, C4, C3, C5, factor B, and properdin were measured in patients with Henoch-Schönlein purpura (HSP). In the cases of acute HSP, 9 of 23 (39%) had a low CH50, and 5 of 17 (30%) a low properdin; C1q, C4, and C3 levels were not depressed. In 10 cases with chronic nephritis following HSP, complement components were normal except for 2 with reduced C4 and one with low properdin. These findings confirm that complement activation occurs in HSP; the low serum levels of properdin in the acute group indicate that there is activation of the alternative pathway in these patients.