Have you ever eaten something without washing your hands or been next to someone who sneezed? If you have then you've been exposed to millions of germs. The world is full of germs (microorganisms) - things like bacteria and viruses which can make us sick - and simple things like breathing and eating are constantly exposing us to them. Sometimes we get sick, but amazingly enough, most of the time we don’t. Our body’s ability to fight off disease is due to the incredible immune system.
Several T cells (white) attacking a tumor
However, at times something goes wrong with the immune system. Everyone gets sick once in a while, and beyond making us ill, there are still many diseases which can kill people. Cancer is a disease which manages to defeat the immune system. But how? For years cancer immunologists assumed that the cells of the immune system simply couldn’t recognize tumor cells. After all, if they could, cancer would be no more serious than the common cold. The many people who die each year from cancer seem to support the view that the immune system is blind to tumor cells. However, new experimental evidence indicates otherwise. As often happens in science the assumed or most obvious view is not always the correct one. In a study designed to investigate exactly how cancerous cells defeat the immune system, a collaborating group of scientists found some very interesting results. In a Nature Medicine journal article titled “Characterization of circulating T cells specific for tumor-associated antigens in melanoma patients” they discovered a phenomenon we have dubbed Dead Cells Walking.
The first problem was to identify anti-melanoma T cells.
To do this they first harvested lymphocytes from the peripheral blood of melanoma patients. Peripheral blood lymphocytes are composed of many different types of immune cells including other T lymphocytes. For example, they contain anti-influenza, anti-cold virus, anti-EBV, and anti-tetanus T lymphocytes (T cell = T lymphocyte).
The next thing was to determine which T lymphocytes were anti-melanoma.
To pull out specific anti-melanoma T cells they prepared MHC-peptides called tetramers.
(Researchers already know that anti-melanoma T cells recognize melanoma peptides presented in MHC, so this is why they made tetramers). MHC tetramers are four MHC-peptide complexes held together, that can bind or label T cells. Only anti-melanoma T cells will recognize and bind to the melanoma peptides in MHC; it is a very specific interaction. This way the researchers knew that they would be finding only melanoma-specific T cells and not other T cells with other specificities. A tetramer flow cytometry experiment allowed enumeration of melanoma specific T cells to learn about Flow cytometry
Although they found a large percentage of T cells specific for a melanoma peptide, those T cells were anergic, so they attempted to stimulate T-cells with IL-2.
The cells were incubated with IL-2 and then tested...