What is the Western Blot?

Mary McMahon
Mary McMahon

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.

If ELISA testing for HIV returns a positive result, the diagnosis is often confirmed through the western blot.
If ELISA testing for HIV returns a positive result, the diagnosis is often confirmed through the western blot.

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.

Western blot is a laboratory analysis famously linked with the diagnosis of HIV.
Western blot is a laboratory analysis famously linked with the diagnosis of HIV.

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.

A western blot is a laboratory analysis technique which is used to isolate proteins.
A western blot is a laboratory analysis technique which is used to isolate proteins.

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.

A blood sample may be used to conduct a western blot.
A blood sample may be used to conduct a western blot.

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.

Understanding how the western blot protocol functions is important for some researchers and lab technicians.
Understanding how the western blot protocol functions is important for some researchers and lab technicians.
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments

sunshined

One of my friends was having symptoms of fatigue and just not feeling very well. It was hard for her to describe what she was feeling, but she knew things weren't right.

She went through all kinds of tests and all of them came back normal. This was good in one sense, but she still didn't know what was wrong.

They finally did a western blot test thinking she might have Lyme disease. It turns out that she did and that was why she was feeling so bad.

She ended up having to go to the hospital for intravenous antibiotics to treat this, and it took a long time before she really felt normal again.

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