Scientists in the U.S. have discovered that children with autism have abnormal immune-system responses and are optimistic that their findings could be used to develop a blood test to screen for the behavioural disorder.
At a conference held in Boston, the 4th International Meeting for Autism Research, two studies which were presented support other research that suggests there are subtle differences in the immune function of children with autism.
Autism is a brain disorder which usually becomes apparent by the time children reach 2 to 3 years of age. It affects an estimated five out of every 1,000 children and has a range of symptoms that include difficulty with social interaction and repetitive behaviours.
The cause of autism is unknown and the majority of experts reject supposed links with childhood vaccines.
The scientists at the conference presented studies which had looked at the blood of children with autism.
In one study, Judy Van de Water of the University of California, Davis, and colleagues separated immune cells from 30 children with autism, and 26 non-autistic children, ages 2 to 5. They mixed in toxins and bacteria.
In the group with autism, the researchers saw, in response to bacteria, lower levels of immune-signalling proteins called cytokines. These children also had irregular responses to a plant protein, but not to other toxins or to measles, mumps and rubella vaccine.
Van de Water said that understanding the biology of autism is crucial to developing better ways to diagnose and treat it.
A second team at the same centre took blood samples from 70 children, ages 4 to 6, with autism, and from 35 other children and the team found that the children with autism had 20-per-cent more immune-system cells called B cells and 40-per-cent more natural killer cells.
They also saw what appeared to be differences in other proteins in the blood. The researchers are still examining that data.
Lead researcher David Amaral says that it is highly likely that there are differences which can be detected in blood samples that will be predictive of the disorder, but they are still some years away from having an actual diagnostic blood test for autism.
Other researchers express caution about testing for autism at an early age. Hilary Cass, a physician who works with autistic children at Great Ormond Street Hospital in London, said there was little evidence that current strategies designed to help two-year-olds with autism work well, with even less known about the benefits for younger children, and as there is no cure the tests will achieve little.
Dr. Amaral says there is a growing view among experts that not all children with autism are 'doomed to autism' at birth, and it may be that some children have a vulnerability, such as a genetic abnormality, and something they encounter after being born, perhaps in their environment, triggers the disorder.
He feels that by studying the biological signs of autism ways may be found to prevent the disorder from ever occurring. Amaral says that even if autism cannot be prevented, intervening early in life, ideally shortly after birth, could greatly improve the lifetime outlook for autistic children.
Dr. Amaral says when viewed from that perspective, "finding a sensitive and accurate biological marker for autism that can be revealed by a simple blood test would have enormous implications".