Objective: Animal models of immune complex mediated tissue injury have shown that tumor necrosis factor (TNF) and TNF induced adhesion molecules play an important role in the pathogenesis of tissue damage mediated by IgG, but not in that mediated by IgA, immune complexes. We compared possible differences in the behavior of 2 TNF induced adhesion molecules (VCAM-1 and ICAM-1) in Henoch-Schönlein purpura (HSP), which is characterized by the formation of IgA immune complexes, versus systemic lupus erythematosus (SLE), which is mostly associated with the vascular deposition of IgG immune complexes.
Methods: Serum concentrations of soluble (s)VCAM-1 and ICAM-1 were determined by ELISA methods in 20 patients with pediatric SLE showing variably active disease, 20 active patients with active HSP, and 19 healthy controls. TNF-alpha as well as p55 and p75 soluble receptors (sTNF-R) were simultaneously tested by enzyme amplified sensitivity immunoassay in 22 patients (12 SLE, 10 HSP).
Results: Serum sVCAM-1 concentration was significantly higher in patients with SLE (mean +/- SD, 608 +/- 76 ng/ml), than in patients with HSP (501.9 +/- 63.3 ng/ml) and controls (446.8 +/- 139.2 ng/ml) (p < 0.001). In SLE patients, sVCAM-1 correlated positively with ESR (r = 0.45, p = 0.02) and negatively with C4 serum levels (r = -0.57, p = 0.004), platelets (r = -0.38, p = 0.03), and lymphocyte count (r = -0.42, p = 0.03). No differences in sICAM-1 serum concentrations were detected among SLE, HSP, or control groups. Soluble VCAM, but not sICAM-1, showed a positive correlation with TNF-alpha (r = 0.71, p = 0.01), p55 (r = 0.63, p = 0.02), and p75 (r = 0.7, p = 0.01) sTNF-R serum concentrations in SLE, but not in patients with HSP.
Conclusion: Our study provides additional evidence of a possible differential involvement of TNF and TNF induced adhesion molecules in the pathogenesis of tissue damage between pediatric SLE and HSP.