London, Apr 22 (IANS): Mental health conditions such as obsessive-compulsive disorder (OCD) could be treated in a new way using drugs that target the immune system, research suggests.

Published in the journal Brain, Behavior and Immunity, the study found that patients suffering from (OCD) have increased levels of a protein called Immuno-moodulin (Imood) in their lymphocytes, a type of immune cell.

"Our findings overturn a lot of conventional thinking about mental health disorders being solely caused by the central nervous system," said study lead author Fulvio D'Acquisto from the University of Roehampton in the UK.

According to the researchers, mice with high levels of this protein was also found to exhibit behaviours that are characteristic of anxiety and stress, such as digging and excessive grooming.

When they treated the mice with an antibody that neutralised Imood, the animals' anxiety levels reduced.

The findings have led the researchers to file a patent application for the antibody and they are now working with a drug company to develop a potential treatment for human patients.

"There is mounting evidence that the immune system plays an important role in mental disorders. And in fact people with auto-immune diseases are known to have higher than average rates of mental health disorders such as anxiety, depression and OCD," D'Acquisto said.

For the findings, D'Acquisto created transgenic mice to over-express this protein in their T-cells, one of the main cells responsible for the development of autoimmune diseases, but found the mice showed more anxiety than normal.

When the research team analysed the genes expressed in the animals' T-cells, they discovered one gene in particular was especially active.

The protein produced from this gene was what they eventually named Immuno-moodulin, or Imood.

When the anxious mice were given an antibody that blocked Imood, their behaviour returned to normal in a couple of days.

The researchers tested the immune cells from 23 patients with OCD and 20 healthy volunteers. They found Imood expression was around six times higher in the OCD patients.

"It is early still, but the discovery of antibodies - instead of the classical chemical drugs - for the treatment of mental disorders could radically change the lives of these patients as we foresee a reduced chance of side effects," he said.