MAC, C5a, C3a, factors B and P (properdin) in patients with active AAV
In patients with active AAV, the median concentrations of MAC, C5a, C3a, and factor B were higher than in the control group (p<0.001 for all comparisons; Table 2). Median properdin level was lower in patients with AAV. However, the difference between the two groups did not reach statistical significance. Concentrations of MAC, C5a, C3a, and factor B exceeded the upper reference levels in 50 (84.7%), 15 (25.4%), 49 (83.1%), and 8 (13.6%) patients respectively, whereas properdin level was decreased in 13 (22.0%) patients.
In 28 patients with AAV, we measured complement components levels both before and following remission induction. Achievement of remission was associated with a significant reduction in C3a from 21436.0 from to 11811.0 ng/ml (p=0.005), a decrease in C5a from 21.6 to 18.8 ng/ml (p=0.035), and factor B levels from 1804.0 to 1480.0 µg/ml (p=0.045). MAC and properdin levels did not change following remission induction therapy (Table 2).
Normalization of elevated complement component levels was achieved in 5 of 8 patients (62.5%) for C5a, in 11 of 25 patients (44.0%) for C3a, in 6 of 24 patients (25.0%) for MAC, and all 6 patients (100%) for factor B. Properdin levels in all 28 patients were normal both before and following remission induction treatment. Of note, in a few patients there was an increase in complement component levels following immunosuppressive treatment, including C3a in 2 patients, MAC in 3 patients, and factor B in 1 patient.