HLA-B27 Anterior Uveitis: Immunology and Immunopathology.

Acute anterior uveitis (AAU) is the commonest type of uveitis and HLA-B27 AAU is the most frequently recognized type of acute anterior uveitis and anterior uveitis overall. Recent evidence indicates that acute anterior uveitis is a heterogenous disease, is polygenic and is frequently associated with the spondyloarthropathies (SpA). Studies of patients with AAU and animal models of disease indicate a role for innate immunity, the IL-23 cytokine pathway and exogenous factors, in the pathogenesis of both SpA and acute anterior uveitis. Recently described genetic associations cluster around immunologic pathways, including the IL-17 and IL-23 pathways, antigen processing and presentation, and lymphocyte development and activation. Patients with ankylosing spondylitis (AS) and AAU share other genetic markers, such as ERAP-1, which show strong evidence of gene-gene interaction and point to new mechanisms of disease pathogenesis. These observations have major implications for understanding the pathogenesis of HLA-B27 diseases, such as AAU, and may lead to the development of more specific therapy for AAU. Received 6 January 2016; revised 6 February 2016; accepted 18 February 2016; published online 31 May 2016.