Autoimmune mechanisms in psoriasis

Psoriasis is a chronic papulosquamous skin disorder affecting 1% to 3% of the general population. There is increasing evidence that immunologic mechanisms are involved in the pathogenesis of psoriasis, and that a link between psoriasis and autoimmunity may exist. A variety of autoantibodies has been observed in psoriasis including antinuclear antibodies, antibodies to small nuclear and cytoplasmic ribonucleoproteins, and antibodies to epidermal cells. UV light treatment of psoriasis may play a role in inducing these autoantibodies in some individuals. Recent evidence that activated T cells in psoriatic plaques may produce interferon-gamma leading to the appearance of ectopic class II major histocompatibility products on the surface of keratinocytes also supports the idea of a link between psoriasis and disordered immunoregulation. The immunologic abnormalities in psoriasis and the association of psoriasis with particular types of autoantibodies raise the possibility that a common etiology may underlie both psoriasis and autoimmunity in some patients, but the different responses of the two diseases to UV light treatment and certain pharmacological agents suggest that psoriasis may not have an autoimmune pathogenesis.