[Immunopathology of psoriasis: from bench to bedside]

Psoriasis is a frequent inflammatory disease that involves mostly the skin and sometimes the joints. This chronic disease is rarely life-threatening but impairs significantly the patient's quality of life. It is characterized, in its typical form, by erythematous and squamous plaques with well-defined borders, associated with increased proliferation of the keratinocytes, inflammation and greater number of dilated blood vessels in the upper dermis. A role of Th1 CD4 T cells was initially suspected. More recently, Th17 CD4 T cells have been shown to play a major role in the disease. It has led to the development of Th17 inhibitors, such as anti-IL-23 (cytokine that induces Th17 CD4 T cell differentiation), anti-IL-17, anti-IL-17RA (IL-17 receptor) and anti-IL-22 (cytokines that are notably produced by Th17 CD4 T cells).