[Comparative characteristics of the complement system in patients with C3-glomerulopathy and atypical hemolytic uremic syndrome of chronic course who suffered an acute episode of thrombotic microangiopathy]

AIM

To compare changes in the complement system in C3-glomerulopathy (C3-GP) and atypical hemolytic uremic syndrome (aHUS) after the relief of an acute episode of thrombotic microangiopathy.

MATERIALS AND METHODS

The study included 8 patients diagnosed with C3-GP and 8 with aHUS in remission. The blood levels of the complement system components were determined: C3, C4, C3a, C5a, factor H (CFH), factor B (CFB), membrane-attacking complex (MAC), antibodies to C3b (anti-C3b-AT), the level of hemolytic activity (CH50), the content of factor D (CFD) in the urine.

RESULTS

C3 and CH50 levels were within the reference range in both groups, however, in the C3-GP group they were at the lower limit, and C3 level was significantly lower than in the aHUS group: 0.56 [0.44; 0.96] vs 1.37 [1.16; 2.52] (p=0.003). CFB increased level was detected in both groups, but in the C3-GP group it was significantly lower than in the aHUS group - 275.1 [222.1; 356.6] vs 438.7 [323.3; 449.3] (p=0.010). C3a, C5a and MAC levels were increased in both groups, but the maximum was in the C3-GP group, and the MAC level in the C3-GP group was 2 times higher than that in aHUS, and these differences reached statistical significance - 123 555±6686 vs 5603±1294 (p=0.036). CFH and CFD levels was increased in both groups, but their highest values was in the aHUS group.

CONCLUSION

Alternative complement pathway activation signs were present in both groups of patients with complement-mediated nephropathies, regardless the stage of the disease. In C3-GP, alternative complement pathway activation was more pronounced than in aHUS after the relief of an acute episode of thrombotic microangiopathy.

[Complement System Abnormalities in Patients with Atypical Hemolytic Uremic Syndrome and Catastrophic Antiphospholipid Syndrome]

Background

The role of the alternative complement pathway (AP) abnormalities in the pathogenesis of aHUS is well studied. Clinical and morphological manifestations of atypical HUS and catastrophic APS are often similar. However, studies on the state of AP in patients with CAPS are virtually absent.

Aims

The aim of our study was to assess the state of AP in patients with CAPS and aHUS. Patients and methods: The study enrolled 67 patients (pts) with a diagnosis of CAPS (28 pts) and aHUS (39 pts). Studies of the complement system are made of 10 pts with CAPS and 20 aHUS. Factor H, I, B, D content, functional activity of factor H, and complement components C3, C4 was determined in serum by ELISA kit.

Results

Patients with CAPS and aHUS showed similar changes in complement biomarkers. The factor H level in the serum was significantly higher than the standard value. However, the specific activity of factor H reduced, mean rate 59% for aHUS and 26% for CAPS. The median value of factor D was twice higher than the normal range in both groups, indicating the activation of the AP.

Conclusions

There are indications of an AP activation not only in pts with aHUS but in CAPS pts too. We suppose that the activity of factor H is a more sensitive indicator of complement system changes than factor H level. Patients with CAPS and aHUS have similar clinical and laboratory characteristics. However, CAPS is more severe, with the involvement of a larger number of vascular beds. Perhaps this is due to the double damaging effects on the endothelium ― of antiphospholipid antibodies (aPL) and activated complement. So we hypothesize that CAPS can be called aPL-mediated TMA in pts with a complement system defect.

[Changes in the complement system in membranoproliferative glomerulonephritis]

AIM

To compare the clinical manifestations membranoproliferative glomerulonephritis (MPGN) in its idiopathic variant, lupus nephritis (LN), and C3 glomerulopathy (C3-GP), by comparing them with changes in the complement system.

SUBJECTS AND METHODS

The clinic of nephrology followed up 42 patients with different types of MPGN in 2013 to 2015. The study included 35 patients divided into 3 groups: 1) 8 patients with C3-GP, 2) 13 with idiopathic MPGN; 3) 14 with Class IV LN. The investigators studied the blood and urine levels of components and markers for activation of the classical and alternative pathways (C3 and C4, С3а, C5a, CFH, CFB, and CFD) of the terminal complement complex (TCC).

RESULTS

The detection rate of C3-GP was 19%. The patients with C3-GP were noted to have the lowest blood concentration of S3 and the highest urinary level of С3а, C5a, TCC, CFH, CFB, and CFD. C3 nephritic factor was detected in 2 patients from the C3-GP (dense deposit disease) group.

CONCLUSION

Alternative complement pathway dysregulation caused by genetic or autoimmune factors plays a leading role in the pathogenesis of C3-GP.