One of the characteristic histologic features of psoriasis is the accumulation of polymorphonuclear leukocytes in the stratum corneum. A major clinical feature of patients with pustular psoriasis or irritated psoriasis vulgaris is migration of polymorphonuclear leukocytes into the skin. The role of polymorphonuclear leukocytes in the pathogenesis of psoriasis is unknown, but a number of observations imply that these cells might be important in the development of clinical lesions.
Recently, there has been tremendous interest in the mechanisms by which polymorphonuclear leukocytes are attracted to the epidermis in psoriasis. Tagami and Ofuji1 have demonstrated that psoriatic scale contains leukotactic substances that appear to be products of complement activation. One possible mechanism for the production of these chemoattractant complement peptides by psoriatic skin could be the release or activation of an epidermal proteolytic enzyme that activates complement by a nonimmunologic mechanism.2 Extracts of parenchymatous tissues and cells are chemotactic
Lazarus GS, Gilgor RS. Psoriasis, Polymorphonuclear Leukocytes, and Lithium CarbonateAn Important Clue. Arch Dermatol. 1979;115(10):1183–1184. doi:10.1001/archderm.1979.04010100003002