Psoriasis in section, erythematous-squamous plaque, hyperkeratosis, hyper-vascularization, inflammation, treatment. Cut of skin with epidermis, dermis, and hypodermis. In the center, a psoriasis plaque showing hyperkeratosis in the stratum corneum with dander, dermoepidermal inflammation and hyper-vascularization of the dermis. Under the influence of antigens, T cells produce pro-inflammatory cytokines and growth factors. Pathological keratinocytes participate in the recruitment of other inflammatory cells. Zoom detailing the pathological keratinocytes with 2 strands of DNA with defects and presence of TNF alpha and interleukins IL12 and IL23. 365 nm UV action site on the DNA strand in the treatment of psoriasis.