Immunopathogenesis of psoriasis: Recent insights on the role of adaptive and innate immunity

Psoriasis is a frequent chronic inflammatory disorder involving mostly skin and joints. Its characteristic features in the skin consist of inflammatory changes in both dermis and epidermis, with abnormal keratinocytic differentiation and proliferation. In recent years, an important set of knowledge has been provided by works addressing the immunopathogenic mechanisms of the disease. Indeed, recent advances in the knowledge of mechanisms linking innate and adaptive immunity have led to reconsideration of the roles of key players in the pathogenesis of the disease. This review will focus on results from studies performed in vitro and in vivo in patients with psoriasis, and on lessons from recently designed animal models which are considered as the most relevant with respect to the human disease. Even more important, these insights provide a rational basis for the design of new therapeutic strategies aiming at the deletion or the down regulation of activated T cells, or at the suppression of pathogenic cytokines such as TNF-α. Some of these new biotherapeutic tools have been successfully used in vivo in clinical trials, providing a confirmation of such concepts.