Boston ? Autistic children have abnormalities in their immune systems and unusual constellations of proteins in their blood that may be an indicator of the disorder, University of California, Davis researchers said Thursday.

The findings “suggest the possibility for future diagnostic tests for autism at birth” and may mean that “we can get children into effective treatment much earlier than is now possible,” said Dr. Helen Tager-Flusberg of the Boston University School of Medicine, who chaired the fourth International Meeting for Autism Research in Boston, where the results were presented.

The findings suggest researchers are beginning to tease out the biological and developmental causes of the disabling disorder, which is now thought to affect as many as one in every 166 children. Autism is a disorder marked by poor language skills, an inability to handle social relations and a lack of connection with the world.

Two groups of researchers from UC Davis reported that autistic children have a dysfunctional immune system, giving them an abnormal response to pathogens and other agents in the environment.

Dr. David G. Amaral and his colleagues collected blood samples from 70 children, ages 2 to 4, who had autism and from 35 children without it. The samples were then studied for concentrations of immune cells, proteins and metabolites from protein processing.

“There were very striking differences at all three levels,” Amaral said. Children with autism had 20 percent more of the white blood cells called B cells and 40 percent more of the variety called natural killer cells.

Amaral speculated the immune abnormalities might be a marker of autism susceptibility that is present at birth, and development of the disorder could require exposure to an environmental trigger.