Background The links between complement and SLE are complicated and fascinating. After many years of study, hypotheses are developing which may begin to explain these apparent paradoxical findings.
Objectives To assess correlation between complement? Circulating immune complexes and organ pathology in SLE.
Methods Of 277 patients enrolled, 252 were female (91%) and the mean age of the patients was 46.6 years (range 18 to 70). 194 patients (70%) had active disease defined as SLEDAI score. All patients met ≥4 ACR SLE criteria. Complement activity in serum was detected by hemolytic method in CH50 units. For the assay of immune complexes (CIC), polyethylene glycol (PEG) precipitation method was used. As a control we used sera from 100 healthy donors.
Results During a long observation of SLE patients we identified variants of hypocomplementemia dynamics. In the group 1 there was almost continuous and increasing hypocomplementemia (75 patients). In the group 2 hypocomplementemia arose during exacerbation of the disease and the complement level was restored under the influence of treatment (67 patients). In the group 3, the activity of complement constantly corresponded to the normal level (135 patients). Glomerulonephritis was diagnosed in 50% of patients in the first group and 46% in the 2nd and in 35.3% in the third group. Renal failure was more frequent among patients in groups 1 and 2. In the group 3, it appeared significantly less often, because of long course of the disease. The average activity of the complement, depending on the group of patients differed, and the average concentration of CIC was highest in the group 3 and in groups 1 and 2 it was statistically less high and was almost the same in both groups. However, signs of inflammation, such as fever and ESR, CRP were higher in patients of the group 3. The activity of complement was the most low and CIC levels were high in patients with renal insufficiency. A decrease of complement activity in patients with the maximum degree of activity of SLE in 56% and 57%, respectively. When calculating the number of units of CH50 per number of units of CIC we get a new integral indicator of the activity of the disease in more than 89% of cases.
Conclusions According to the activity of the complement system in SLE represents a heterogeneous group. The low level of activity of the complement system, characteristic for a certain group of patients contributes to the appearance of glomerulonephritis. High level of complement has a protective effect against renal pathology. The ratio of activity of the complement system and the level of circulating immune complexes has a specific pathogenic role in SLE.
Disclosure of Interest None declared