DIFFERENCES IN TUMOR-NECROSIS-FACTOR-ALPHA SOLUBLE RECEPTOR SERUM CONCENTRATIONS BETWEEN PATIENTS WITH HENOCH-SCHONLEIN PURPURA AND PEDIATRIC SYSTEMIC LUPUS-ERYTHEMATOSUS - PATHOGENETIC IMPLICATIONS

Objective, Animal models of immune complex mediated tissue injury have shown different patterns of proinflammatory cytokine production accor ding to the subtype of immunoglobulin involved. The IgA immune complex model differs from the IgG model by the lack of involvement of tumor necrosis factor (TNF) in the pathogenesis of tissue damage. We investi gated in age matched patients the possible difference in TNF involveme nt in a predominantly IgA mediated disease, Henoch-Schonlein purpura ( HSP), in comparison with systemic lupus erythematosus (SLE), in which vascular injury is mostly associated with local deposition of IgG immu ne complexes. Methods, Serum concentrations of TNF-alpha and its solub le receptors (sTNF-R) p55 and p75 were studied in 20 patients with ped iatric SLE at various degrees of disease activity, in 16 patients with highly active HSP, and in 15 healthy controls by enzyme amplified sen sitivity immunoassay. SLE disease activity was evaluated using 2 score s, the European Consensus Group Study for SLE Disease Activity Criteri a and the SLE Disease Activity Index. Results, Serum concentrations of TNF-alpha fell within the normal range in patients with both SLE and HSP irrespective of disease activity. Conversely, patients with SLE di splayed increased serum levels of sTNF-R that correlated positively wi th the degree of disease activity (r = 0.60, p < 0.001; r = 0.71, p < 0.001, for p55 and p75, respectively). In contrast, no difference in t he serum levels of sTNF-R was found between patients with highly activ e HSP and controls Conclusion, Our study provides the first circumstan tial evidence that pediatric SLE and HSP are characterized by differen tial involvement of TNF in the pathogenesis of tissue damage.