The immunologic basis for the treatment of psoriasis with new biologic agents.

Psoriasis vulgaris is the most prevalent T-cell-mediated inflammatory disease in humans. The pathogenesis of psoriasis is linked to activation of several types of leukocytes that control cellular immunity and to a T-cell-dependent inflammatory process in skin that accelerates the growth of epidermal and vascular cells in psoriasis lesions. Critical steps in immunologic activation include Langerhans cell maturation (activation), T-cell activation, differentiation and expansion of type 1 T cells, selective trafficking of activated T cells to skin, and induction of an inflammatory cytokine and chemokine cascade in skin lesions. In turn, each of these steps offers an opportunity for intervention with engineered biologic therapeutics.