July 18, 2012
Immune Irregularities Linked To Autism
Connie K. Ho for redOrbit.com — Your Universe Online
Researchers at the California Institute of Technology (Caltech) recently unveiled findings from a new study which showed that certain changes in an overactive immune system of mice could cause behaviors similar to those found with autism. In some cases, activation can be related to what is experienced by a developing fetus in a womb.About a decade ago, the scientists of Caltech helped lead the research on the connection between irregularities in the immune system and neurodevelopmental disorders like autism. The new study answered the question on how changes in the immune system helped cause the development of autism or was a side effect of the disease. The findings are featured in this week´s edition of Proceedings of the National Academy of Sciences (PNAS).
"We have long suspected that the immune system plays a role in the development of autism spectrum disorder," explained lead researcher Paul Patterson (www.its.caltech.edu/~phplab/phplab.html), the Anne P. and Benjamin F. Biaggini Professor of Biological Sciences at Caltech, in a prepared statement. "In our studies of a mouse model based on an environmental risk factor for autism, we find that the immune system of the mother is a key factor in the eventual abnormal behaviors in the offspring."
In the new study, the team of investigators first focused on creating a mouse model that connected autism-related behaviors with immune irregularities. Based on other studies that showed that there was a relationship between viral infection and the first trimester of a mother´s pregnancy for a higher risk of autism spectrum disorder, they injected mice that were pregnant with a viral mimic that would jumpstart the same immune response that a viral infection would.
"In mice, this single insult to the mother translates into autism-related behavioral abnormalities and neuropathologies in the offspring," remarked lead author Elaine Hsiao, a graduate student in Patterson's lab, in the statement.
The scientists saw how the offspring had behavioral symptoms that were related to the autism spectrum disorder. Those who are on the autism spectrum generally show repetitive or stereotyped behavior, fewer social interactions, and difficult communication skills. In the mice, the actions translated to excessive self-grooming, compulsive burying of marbles, vocalizing less often or in a different manner, and spending more time with a toy than other fellow mice.
After understanding the behaviors of the mice, the researchers looked at the immune changes. These immune irregularities were similar to those seen in people who were diagnosed with autism, such as a lower level of regulatory T cells. These immune changes all led to an immune system that was working nonstop, which led to inflammation.
"Remarkably, we saw these immune abnormalities in both young and adult offspring of immune-activated mothers," commented Hsiao in the statement. "This tells us that a prenatal challenge can result in long-term consequences for health and development."
Lastly, the scientists examined if the immune problems would affect autism-related behaviors. They were able to fix several of the autism-like behaviors by offering the offspring a bone-marrow transplant from regular mice. The normal stem cells helped refuel the immune system of the host animals and change the autism-like behaviors.
Based on their work with mice, the researchers believe that the results cannot be completely be compared with humans. They still need to investigate whether an infusion of stem cells or the bone marrow transplant procedure helped correct the behaviors. The study showed how immune irregularities in adolescents could be a possible target for treating behaviors related to the autism spectrum disorder. In furthering the study, the scientists want to analyze the effects of highly targeted anti-inflammatory treatments on mice that have autism-related behaviors and immune irregularities.