In situ Expression of CD40 and CD40 Ligand in Psoriasis

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Abstract
Background: The interaction between CD40 and CD40 ligand (CD40L) provides a signal that contributes to the initiation of cellular immune responses. However, little information on the in vivo expression of CD40 and CD40L in cutaneous inflammation has been reported. Objective: To investigate the potential role of CD40-mediated signals in the pathogenesis of psoriasis. Materials and Methods: In situ CD40 and CD40L expression was examined immunohistochemically in different stages of psoriatic lesions: fully developed and initial pinpoint. Results: In normal skin, faintly positive immunoreactivity for CD40 was seen in the basal keratinocytes and dermal endothelial cells. These showed almost the same intensity as that seen in psoriatic lesional skin. In the dermal infiltrates of psoriatic lesions, CD40 was intensely expressed and some of these positive cells appeared to be dendritic in shape. Whereas CD40 expression was observed almost in all specimens of psoriatic lesions, the expression of CD40L was predominantly detected in the initial pinpoint lesions of psoriasis. These seemed to be distributed close to CD40-positive cells. Conclusion: These results suggested that CD40L-triggered signals could be involved in the early stage of psoriatic lesion formation.