Autoantibodies and Resident Renal Cells in the Pathogenesis of Lupus Nephritis : Getting to Know the Unknown
Sera from 45 patients with lupus nephritis (LN), 63 patients with immunoglobulin A nephropathy (IgA N), and 71 glomerulonephritic controls (including 44 mesangial proliferative glomerulonephritis cases, 14 membranous glomerulonephritis cases, and 13 focal segmental glomerular sclerosis cases), and from 33 normal control subjects were tested by a cellular enzyme-linked immunoabsorbent assay for their anti-endothelial cell antibody (AECA) activity. Compared with normal controls, AECAs of the IgG subtype (AECA-IgG) were detected in LN (P < 0.001) and AECAs of the IgA subtype (AECA-IgA) were detected in both IgA N and LN (P = 0.018 and P < 0.001, respectively). Binding activity of AECA to endothelial cells was inhibited by endothelial cell lysate and fibroblast lysate but not by lymphocyte lysate, double stranded-DNA, or bovine serum albumin. Anti-endothelial cell antibody-positive sera also reacted with fibroblasts. In IgA N, associations were found between the presence of AECA and younger age (P = 0.036), proportion of crescents greater than 10% (P = 0.016), fibrin crescents (P = 0.016), and focal and segmental necrotizing lesions (P = 0.047). In LN, inverse associations were found between the presence of AECA and the duration of disease (P = 0.021), elevated serum creatinine levels (P = 0.020), decreased creatinine clearance (P = 0.043), and frequency of chronic renal failure (P = 0.036). Positive associations were observed between the presence of AECA and active lupus (P = 0.017), anti-nuclear antibodies (P = 0.015), and anti-DNA antibodies (P = 0.041). Our results suggest that AECA may be linked with the pathogenesis of LN and IgA N.