Infectious Uveitis, Mechanisms and Immunopathology

It is important to distinguish infectious uveitis from noninfectious one for early treatment. Bacteria, viruses, fungi, parasites are the causes of infectious uveitis. Bacterial diseases causing uveitis are mainly syphilis, tuberculosis, Lyme disease and brucellosis. HIV, HSV, VZV, CMV, EBV, measles and rubella are the frequent viral causes. The most common fungal uveitis causes are Candidiasis, Aspergillosis, Cryptococcosis and Histoplasmosis. It is now widely accepted that uveitis is not caused by direct infectious agents, and that microorganisms alter immüne response leading to autoimmune and inflammatory diseases. The mechanism observed in immunopathogenesis is the destruction of retinal visual cells due to an irreversible CD4 T cell response. The Th1 cells reach the target retinal tissue from the peripheral lymphoid system for specific retinal autoantigens and cause changes in photoreceptors, leading to an increase of Th1 cytokines by an inflammatory reaction in the uveitic eyes, whereas the cytokines of Th2 increase in the later stages. In addition to Th1 cells, Th17, regulator T cells, cytokines, autoantibodies and neutrophils are also discussed in immunopathogenesis.