CD8A and psoriasis: Immunophenotyping of psoriatic lesions showed a mixed T-cell population (CD4 and CD8) and Langerhans cells distinct from normal skin.[16] This cellular infiltrate changed with topic or systemic treatment.[17, 18] In another study, biologic therapy failure ruled out the major participation of the humoral immune system in psoriasis immunopathology.[19] Thus, the cellular arm of the immune system was implicated in psoriasis for the first time during the 1980s.[20]