Skin is alive : epidermis basal cells multiply, change aspect, and migrate towards the surface.
There they become keratinocytes and desquamate
Epidermal basal cells
Normals : The epidermis basal cell takes 30 days to become a keratinocyte
Psoriasis patients : the basal layer cell only takes 4 days to become a keratinocyte.
This leads to an enhanced number of keratinocytes (desquamation) and is associated with an increased activity of Tlymphocytes in the epidermis(carrying CD 58 & CD 11 membrane receptors), and to an increased production of TNF