OX40 ligand and OX40 are increased in atopic dermatitis lesions but do not correlate with clinical severity.

Background: The interaction between the OX40 ligand (OX40L) and OX40 has been suggested to have pathogenetic significance in atopic dermatitis (AD).
Objective: The purpose of this study was to investigate the expression and relevance of OX40L and OX40 in AD skin.
Methods: OX40L and OX40 were stained immunohistochemically on the cryosections of the lesional and non-lesional skin of 17 subjects with moderate-to-severe AD and of 10 patients with psoriasis vulgaris. Phorbol myristate acetate (PMA) stimulated keratinocytes and cell membrane preparations from PMA-stimulated keratinocytes or LAD-2 mast cells were incubated with peripheral blood mononuclear cells (PBMC) in the presence or absence of blocking monoclonal antibodies to OX40L, CD30L or ICAM-1.
Results: We show for the first time that the staining intensity of OX40L and the number of OX40(+) cells are significantly greater in the lesional dermis than in the healthy-looking dermis in AD (P < 0.001 in both comparisons) and also in psoriasis (P = 0.01 and P < 0.001 respectively), but neither molecule correlate significantly with the clinical severity of AD. Living keratinocytes and cell membranes from LAD-2 mast cells and keratinocytes increased the PBMC proliferation response. Anti-OX40L antibody inhibited, in a similar fashion as anti-ICAM-1 and anti-CD30L, PBMC proliferation induced by LAD-2 membranes, but stimulated that induced by keratinocytes.
Conclusion: Our findings provide evidence for the involvement of OX40 and OX40L in the pathogenesis of AD though they are not specific to AD and in vitro results suggest complex interaction.
(© 2012 The Authors. Journal of the European Academy of Dermatology and Venereology © 2012 European Academy of Dermatology and Venereology.)