[The lymphocyte: protagonism in the new era of the biological therapies].

Psoriasis is a systemic type T cell mediated immune system chronic inflammatory skin disease. These cells play an important role in the immune system and in the inflammatory response that determines the development and maintenance of the psoriasis lesions. However, greater understanding of the pathophysiology of this disease has led to the development of specific and selective biological treatments. Efalizumab is a humanized IgG1 monoclonal antibody that binds to the Leukocyte-Function-Associated Antigen 1 (LFA-1). When it binds to the CD11a--alpha subunit of LFA1--it inhibits the binding of this ligand to the intercellular adhesion molecule 1. This inhibits several processes related with the T cells that are fundamental in the pathogenesis of psoriasis: activation of the T cells in the lymph nodes, the migration of the T cells towards the dermis and epidermis and finally the reactivation of these in the inflammatory focus. The clinical studies have demonstrated that efalizumab, administered subcutaneously only once a week, provides a clinical benefit as well as improvement in the quality of life in patients with psoriasis with chronic, moderate or severe plaques. Long-term treatment studies suggest that continuous therapy with efalizumab is more beneficial in the maintenance of the improvement of the response and demonstrate that efalizumab may be administered safely for prolonged periods. Given its efficacy, rapid onset action, safety profile due to its selective action mechanism and convenience in its subcutaneous self-administration weekly, efalizumab offers a new therapeutic option, especially of interest for the treatment of psoriasis.