Introduction to autism:
Autism spectrum disorder is a developmental disease that results in impaired functioning in social communication and abnormal behaviors. People with autism generally use less eye contact, fail to know when or when not to use non-verbal gestures, and fail to recognize the emotions of others. Abnormal behaviors seen in autism include but are not limited to repetitive ritualistic behaviors, extreme interests in specific topics, and a need for unvarying routine. While it is difficult to draw the line between a normal and abnormal brain, research has suggested evidence that with autism spectrum disorder there are differences in neurochemical pathways that limit normal functioning of people with the disease.
Environmental causes:
The complex interaction among neural processes associated with autism begins early in development. During pregnancy, even slight changes in the environment can result in tremendous change in the development of the child. A pregnant mother could become infected with a minor pathogen and pass the infection on to the child through the placenta. This transfer may induce a change in the child’s immune response resulting in excess inflammation. Unfortunately, there is only so much preventative action mothers can take during pregnancy. Proper nutrition and avoidance of harmful chemicals and pathogens is all a mother can do to diminish problems with development. It is important for mothers to know that everything they do could in some way affect the baby, but it is also important to know that it is impossible to reduce all environmental risks down to nothing. Along with countless environmental factors associated with ASD, numerous genes have also been identified.
Genetic influences:
Thousands of genes have been linked to ASD creating a nightmare for scientists trying to fully understand why this disease occurs. One of the most common genetic abnormalities seen in ASD is a mutation in the MECP2 gene. This gene codes for a protein used in regulating the transcription of other genes. It helps to regulate synapse formation in the brain and makes sure that only necessary connections are made in the brain. People who have an alteration in this gene will have abnormal connections of neurons causing miscommunication among brain domains. Related to this gene is the process seen with the mTOR pathway. In this pathway, unused connections of the brain are removed allowing for normal communication between neurons. This pruning process is essential in normal brain functioning and it thought to be severely impaired in autism resulting in an unusually high density of neurons.
The role of the immune system:
The immune system plays a large role in both in peripheral body tissue and the nervous system. It is used to eliminate intruding pathogens and rid the body of any harmful substances. To do this, a close interaction of T and B cells is orchestrated. T-cells are a type of white blood cells used in initiating an immune response. They release chemicals that cause inflammation and notify the rest of the body where the infection is. These cells are also used in the destruction of harmful pathogens and infected cells. B-cells release antibodies that attach to invading substances and mark them for destruction by T-cells. It is thought that an abnormality of this general process in the brain leads to symptoms associated with autism. Careful regulation of these cells allows normal brains to eliminate harmful substances while preserving delicate brain tissue. In autistic brains, however, regulation of these immune cells is hindered causing excess inflammation. It is this point where many aspects of autism are thought to arise. The extra chemicals in the brain causes excess inflammation without enough regulation. From here, abnormalities in other brain processes are initiated leading to permanent damage during development.
Conclusion:
The pathophysiology of autism is extremely complex and difficult to map out. There are many different aspect of the disease that affect different pathways in neurochemistry. While we do know many of these parts and how they interact with each other, the exact order of events remains unknown. Perhaps genetic predispositions lead to higher probability of in utero infection leading to a malfunctioning immune response in the brain etc. Or perhaps the pathophysiology is much less linear and requires interaction between different processes all at once. Nevertheless, a complete understanding of ASD may never be reached but further research on the disease could provide helpful insight for prevention and treatment of ASD.
