A team of researchers has determined that variations in certain genes involved in fighting infection can successfully predict the risk of developing age-related macular degeneration, the leading cause of blindness in Americans over the age of 60.

The team, led by Bert Gold, Ph.D., and Michael Dean, Ph.D., of the National Cancer Institute, part of the National Institutes of Health, identified a genetic variant that is associated with an increased risk of developing age-related macular degeneration. (AMD). They also found two genetic variants that protect against developing this disease.

The genes analyzed in this study — Complement Factor B (BF) and Complement Component 2 (C2) — contain the instructions to make proteins that activate the body's immune defense against microbial infections. These defense responses are part of a system called the complement pathways. These pathways involve numerous proteins in the blood that work in association with the body's immune cells and antibodies to destroy bacteria, viruses or fungi invading the body. Some complement proteins can stimulate inflammation, the redness and swelling that result in tissues when they are infected.

Previous studies have shown that genetic variations in complement pathway genes can cause a dysfunction in the inflammatory response that plays a central role in the pathology of AMD.

Data analysis revealed that specific variants in each gene were associated with AMD. One genetic variant conferred an increased risk for AMD, while two genetic variants showed protection against developing this disease. These results, when analyzed in association with results linking AMD and genetic variants of Complement Factor H — a gene than contains the instructions to make a protein that inhibits the complement system — showed that 56 percent of the unaffected individuals had a variant that conferred protection to AMD while 74 percent of those with AMD had no protective variants.

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Approximately 7.3 million Americans have intermediate stages of AMD with a high risk of increasing vision loss, while 1.8 million are visually impaired due to this disease.

There is no known cure for AMD.

The National Eye Institute (NEI) conducts and supports research that leads to sight-saving treatments and places a key role in reducing visual impairment and blindness.