Immune response genes in uveitis.

Uveitis is defined as an intraocular inflammation induced by different etiologies. Though the precise pathogenesis is still unknown, accumulating evidence shows that both innate and adaptive immune responses may be predominant mechanisms involved in the development of uveitis. Toll-like receptors have been shown to be expressed in the human eye and play an important role in infectious uveitis. The NOD proteins, expressed mainly in the cytosol by APCs, recognize the products of bacteria and participate in the development of uveitis. HLA genes have been associated with some uveitis entities, including acute anterior uveitis (HLA-B27), Behcet disease (HLA-B51), birdshot retinochoroidopathy (HLA-A29), Vogt-Koyanagi-Harada syndrome (HLA-DR4), sarcoidosis, sympathetic ophthalmia, juvenile idiopathic arthritis, tubulointerstitial nephritis and uveitis (TINU) syndrome, and pars planitis (HLA-DR15). The exact mechanism whereby certain HLA genes predispose to a certain uveitis entity has not yet been elucidated. In addition, several studies have demonstrate that polymorphisms in certain immune response genes, such as tumor necrosis factor (TNF), MHC class I polypeptide-related sequence A (MICA), interleukin-1 (IL-1), and some chemokines, may contribute to the development of human uveitis. Polymorphisms in the gene coding for the costimulatory molecule known as cytotoxic T-lymphocyte antigen 4 (CTLA-4) were recently found in Chinese patients with VKH syndrome but not in patients with Behcet disease. Further developments in the unraveling of immune response genes may lead to a better understanding of human uveitis and will hopefully allow the development of novel treatment regimes.