Early inflammatory changes in the "perilesional skin" of psoriatic plaques: is there interaction between dendritic cells and keratinocytes?

Early inflammatory changes in psoriatic plaques were investigated immunohistochemically by studying the normal-appearing skin adjacent to the plaques (perilesional skin), lesional skin, and distant uninvolved skin from psoriasis patients. Perilesional epidermis contained numerous CD1a-positive Langerhans cells, some of which expressed HLA-DR, CD83, CD80, and CD86, at the same time expressing Langerin. There were also numerous CD83-positive, CD11c-positive, Langerin-negative dendritic cells (DCs) in the epidermal–dermal junction of perilesional skin. CD3-positive T lymphocytes were sparse in the perilesional skin. Perilesional epidermis expressed keratin K6 and K16, inflammatory keratins, and C/EBP β , a transcription factor related to inflammatory cytokines. Our results demonstrated the abundant distribution of activated DCs in the perilesional skin of psoriatic plaques, where early inflammatory changes occur in the epidermal keratinocytes, which suggests their involvement in the provocation of epidermal inflammation in the perilesional epidermis and further pathogenic roles in the formation of psoriatic plaques.