Sunday, March 25, 2012

Biomarker indicating autism found in patients' blood

By learning more about the mechanisms underlying a disease, we discover which molecules are responsible for the symptoms we observe. Often, proteins are disturbed in their function and behave in a way that damages the body. When we know which proteins indicate disease, that information can be used as a diagnostic tool. Measuring protein levels can indicate disease, sometimes even before symptoms actually manifest. We call such proteins biomarkers, and scientists managed to find one that seems to be an indicator for autism.

In an effort to find out whether there are things in the blood that may indicate autism, scientists compared blood samples of patients with a group of healthy people. A spectrometer was used to analyse blood samples for protein patterns. With this, the differences between the two groups would indicate that a certain protein was altered in the disease and can serve us as a biomarker. The researchers, working at different labs in Sweden and Iran, concluded after their analysis that a protein called C3 differs in patients with autism. To be precise: three parts of the C3 protein were found to be lower in concentration in those who are diagnosed with autism.

Immune system
Peculiar enough, C3 is involved with the immune system, where it is part of a pathway that builds a offensive structure after recognizing threats such as microbes. After a foreign threat invades the body and infects cells, C3 plays a central role in setting up a pathway that eventually leads to the formation of something called a membrane attack complex. This structure, consisting of various molecules in the so-called complement system in which C3 plays a part, binds to infected cells and destroys its membrane. Consequently, the infected cells die.
The complicated pathways of the complement system. It starts with recognition of foreign particles on the cellular surface (in the three yellow boxes). C3 plays a central role and is necessary for all pathways. Eventually, by interactions between several proteins, a structure is formed that can destroy cellular membranes (right bottom, consisting of various Cx proteins)
From the experiments, it is clear that a particular protein in a particular defensive mechanism is affected in autism. However, because it is a neurological disease characterized biologically by faulty brain wiring, its relationship with C3 is not quite clear. Previous studies did find, on a genetic level, involvement of the complement system in autism. Scientists in the present study have demonstrated it is also measurable on a protein level, which is important to develop a diagnostic test that makes use of biomarkers. More studies are required to find out how autism relates to the complement system, but it does seem we are getting closer to developing an independent diagnostic tool for a disease with psychological symptoms.

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