A western blot is a laboratory analysis technique which is used to isolate proteins. It can be used in the diagnosis of certain diseases, and also in research on various proteins and processes. Famously, the western blot is linked with diagnosis of HIV infection, but it can also be used to look for traces of bovine spongiform encephalitis (BSE) and Lyme disease. Samples sent out for testing with a western blot protocol can return results in a few days to several weeks, depending on the lab capacity and the urgency.
In a western blot, the sample, which can be from blood or tissue, is first put through electrophoresis so that the proteins will separate out by length. A strip of the electrophoresis gel with isolated proteins of the target length can be used to transfer the proteins to a nitrocellulose substrate for the next stage of the test. During this stage, an antibody is introduced to the sample, with the goal of tagging the proteins with antigens which that antibody locks on to.
Once the proteins have been tagged, they can be easily identified. In the case of testing for disease, the presence of a reactive protein indicates that the sample has tested positive. Western blots rarely return false positives, although it can happen on occasion, and they may also return false negatives, in which a person actually has a disease, but it does not show on western blot testing. This can be especially common in cases when the disease-causing agent has not yet started to replicate.
Researchers can use the results to identify specific proteins which they are tracking, and for a variety of other purposes. Understanding how the western blot protocol functions is an important skill for some researchers and laboratory technicians, as they must be able to return reliable and dependable results using this method. Lab skills including learning how to handle complicated or bad samples, and how to avoid contamination during the process so that the results of the test are known to be true.
This technique is sometimes known as an immunoblot, because essentially the desired proteins are “blotted” with antibodies so that they will show up. This test can be used to look for proteins in all animals, not just humans, with veterinarians often using the western blot test to determine whether or not a herd of cows has been infected or exposed to BSE.