[Immune mechanisms in retinal degeneration]

Hereditary retinal dystrophies are characterised by a common apoptotic pathway leading to progressive retinal degeneration. Similar degenerative processes are evident in multifactorial and complex retinal disorders including age-related macular degeneration. To understand early triggers of these mechanisms, genetic and experimental mouse models have been developed that mimic various forms of human retinal degeneration. In most of these models, early chronic activation of the innate immune system has been documented. This process mainly involves the complement cascade as humoral component and microglial cells as sensors and effectors of the retinal immune response. Current evidence suggests that the genetic predisposition and individual factors like age or diet critically influence the immune homeostasis in the retina. Based on their effectiveness, innate immune mechanisms are thought to support or even provoke retinal degeneration. This review article summarises recent progress in understanding the role of innate immunity in retinal degenerative diseases. We especially focus on human studies and attempt to provide a link between activation of the complement system and microglial function. Moreover, concepts are presented that highlight the retinal immunopathology as potential therapeutic target to prevent vision loss.