Serum OX40 ligand: a potential marker of atopic dermatitis disease severity in children

Background: OX40 ligand (OX40L) and OX40 are members of the tumor necrosis factor (TNF) and TNF receptor (TNFR) super families respectively. Recent studies have indicated the critical involvement of OX40/OX40L interaction in the pathogenesis of atopic dermatitis. To our knowledge, no data could be cited in literature concerning OX40L levels in serum or in other biological fluids of atopic dermatitis children. Objective: This study was done to explore the expression of OX40L in the serum of atopic dermatitis children with respect to disease activity and severity. Methods: This follow-up, case-control longitudinal study was conducted on 64 children as a stratified non-random sample; 34 with atopic dermatitis and 30 healthy children. Serum concentrations of OX40L were measured by sandwich enzyme immunoassay. The severity of atopic dermatitis was assessed according to the Leicester Sign Score (LSS), Simple Scoring System (SSS), Scoring Atopic Dermatitis (SCORAD) index, and Objective SCORAD. Results: Serum OX40L levels (pg/ml) in atopic dermatitis patients were significantly elevated as compared to controls (176.6 +/- 45.9) whether during flare (1007 +/- 241.5) or quiescence (699 +/- 198.5). There were significant positive correlations between serum OX40L levels and each of the LSS, SSS and SCORAD indices of atopic dermatitis disease severity, while it was insignificant regarding the objective SCORAD. However, when atopic dermatitis children were classified according to the objective SCORAD index of severity into mild, moderate and severe, it was found that the mean serum level in the severe group was significantly higher than the corresponding values of the mild or the moderate group. OX40L levels did not correlate with serum total IgE or absolute eosinophils count. Serum total LDH levels correlated positively with each of the serum OX40L levels and the LSS and SCORAD indices of severity. Conclusions: Serum OX40L level is an objective reliable marker of atopic dermatitis severity in children. It may be useful for follow up and may help to improve research and management of this disease. Blockade of interactions between OX40 on Th2 cells and OX40L on activated dendritic cells using an OX40L-specific monoclonal antibody could represent a novel strategy for the treatment of atopic dermatitis.