Researchers say their new findings could lead to targeted therapies for conditions like ulcerative colitis, multiple sclerosis, rheumatoid arthritis, and celiac disease.

Many autoimmune disorders are believed to be passed down from parents to children, and researchers are closer than ever to unlocking the genetic secrets of their transmission.

Researchers at the National Institute of Aging (NIA) have honed in on five of 89 independent variations in human genetics that are believed to be responsible for autoimmune conditions, from celiac disease to multiple sclerosis, in which the body’s defense system mistakenly attacks itself.

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A new study, part of the SardiNIA Study of Aging, shows these gene variants are associated with how the body produces immune system cells, in addition to contributing to autoimmune disorders. The study will be published in the forthcoming issue of the journal Cell.

The researchers discovered that variations in these particular genes have “very significant effects” on the number of specific immune system cells the body produces.

“We know that certain diseases run in families. From this study, we wanted to know the extent to which relative immune resistance or susceptibility to disease is inherited in families,” David Schlessinger, chief of NIA’s Laboratory of Genetics, said in a statement accompanying the study. “If your mother is rarely sick, for example, does that mean you don’t have to worry about the bug that’s going around? Is immunity in the genes? According to our findings, the answer is yes, at least in part.”

Your genes, the researchers say, affect the number of cells in your adaptive immune system, the kind that learns to respond to pathogens by producing, storing, and transporting specific defensive cells and molecules. While our immune system has evolved over generations to reject some pathogens and cancers, too many of these immune defenders can increase a person’s chance of developing specific autoimmune disorders.

To come to these conclusions, the NIA examined genetic data from the SardiNIA study, which involves about 8.2 million gene variants in blood samples taken from 1,629 people living on the island of Sardinia. Researchers are focusing on Sardinians because their lineage can be traced back 20,000 years to when the Mediterranean island was first settled.

“We have learned that, in case after case, findings in Sardinia have been applicable world-wide,” said Dr. Francesco Cucca, director of the National Research Council’s Institute of Genetic and Biomedical Research in Italy.

Researchers believe understanding the genetic component of the body’s immune response could someday allow for personalized therapies to treat an overactive immune system response.

Biologic, immunosuppressive drugs currently on the market can help people with certain autoimmune disorders, such as Crohn’s disease and psoriasis, but they are often ineffective or come with unwanted side effects, such as an increased risk of infection.

While diseases can be passed down from parent to child, that doesn’t automatically mean you’ll get the disorders your parents suffer from.

Many autoimmune diseases are brought out by other risk factors, some of which are preventable. The most common preventable aggravators of autoimmune diseases include infections, smoking, and heavy alcohol consumption.

A recent study published in the journal Nature linked a high-salt diet to the increased likelihood of developing an autoimmune disorder.

Autoimmune disorders can also be risk factors for other diseases. One recent study concluded that autoimmune disorders and infections during childhood are risk factors for mood disorders, such as depression and bipolar disorder.