TNF and psoriasis: The numberof mast cells is increased in psoriatic lesions, mainly in the subepidermalconnective tissue.7 There areevidence that histamine release via adenosine receptors promote a negativefeedback, signaling TNF-alpha production by macrophages, and theninflammation.1Furthermore, mast cells alone can activate other mediators that can affect theimmune system and promote inflammation.7 Psoriasis patients present an increase in theexpression of a factor called "stem cell factor (SCF) kit ligand", responsiblefor the migration, activation, and maturation of mast cells.7