Background Immune deposits for immunoglobulin (Ig) classes (IgG, IgM and IgA) and complement components (C3 and C1q) are a main feature of lupus nephritis (LN). The glomerular intensity of these deposits can be associated with the pathogenesis and prognosis of LN.
Objectives The main objective of this study was to evaluate the association of the intensity of Ig and complement deposits with activity, chronicity (Austin et al.1) and the classes of LN (ISN/RPS classification).
Methods Registries of all biopsies of LN performed the last five years were evaluated. All biopsies were classified according to the ISN/RPS classification; immunofluorescences were semi-quantitatively graded from 0 to 4 according to the intensity of fluorescence. Activity and chronicity indices (AI and CI) were recorded for proliferative classes (class II, IV or their combinations) according to Austin et al.1 Correlation was evaluated through Spearman's rho (r), and non-parametric statistics were performed for continuous variables.
Results We included 90 biopsies of LN patients: 3 class I, 4 class II, 7 class III, 15 class III/V, 29 class IV, 17 class IV/V and 15 pure class V. For the 68 proliferative LN biopsies (class III, IV and combination with V) the median (IQR) activity was 7 (4-11) and chronicity 3 (1-5). Ig and complement deposits were similar between the classes of LN. Correlation between activity and intensity of Ig or complement components were: IgM r=0.35 (p=0.006), IgA r=0.0211 (p=0.873), IgG r=0.069 (p=0.599), C1q r=0.239 (p=0.065), and C3 r=0.168 (p=0.195). Correlation between chronicity and Ig or complement components were as follows: IgM r= -0.109 (p=0.384), IgA r=0.295 (p=0.017), IgG r=-0.132 (p=0.288), C1q r=-0.136 (p=0.276), C3 r= -0.200 (p=0.104). Figure 1 shows the positive association between IgM and activity of LN.
Conclusions The positive association between activity of LN and IgM, suggests that this immunoglobulin may participate in both prognosis and the histologic changes described for activity of LN such as proliferation, cellular crescents, interstitial inflammation and others.
Austin H, et al. Kidney Int 1984;25:689-95
Disclosure of Interest None declared