New York, July 30 (IANS): Women and men use different switches to turn on many immune system genes, a new Stanford University study has revealed.

Researchers said the new findings might explain the much higher incidence in women of autoimmune diseases such as scleroderma, lupus and rheumatoid arthritis.

Some genes are virtually always on, while others sit unused for years at a time.

Some genes can be always on in one person and always off in another. A minority of genes switch on and off.

The new study found that the genes that switch on and off differently from person to person are more likely to be associated with autoimmune diseases.

The study, published in the Cell Systems journal, took ordinary blood samples from 12 healthy volunteers to measure how certain genes are switched on and off, and how that measure varied from individual to individual.

Across the 12 healthy volunteers, seven percent of the genes were switched on in different patterns from person to person. For each person, these patterns persisted over time, like a unique fingerprint.

"But the single greatest predictor for genes' tendency to turn on and off was the sex of the person. In terms of significance, sex was far more important than all the other things we looked at, perhaps even combined," the study's senior author professor Howard Chang said.