Do White Blood Cells kill cancer cells?
1 Answer
No; that function is reserved for cytotoxic T cells and natural killer cells.
Explanation:
Okay, there is an extremely complex process involved here, and it involves the immune system's ability to recognize "self vs. not-self". Essentially, it means that the immune system has the ability to recognize what cells are part of you, what cells are actually pathogens such as bacteria, and even what cells have become cancerous.
The recognition of cancer cells is done, not by white blood cells, but by specialized lymphocytes that are able to interact with cells in the human body and see if they are functioning properly. These lymphocytes are cytotoxic T cells and natural killer (NK) cells
How do these cells do this? They check for specific cell membrane surface proteins known as major histocompatibility complex type I (MHC I) proteins. Normal cells produce normal MHC I proteins, which the cytotoxic T cells will interact with. The chemical interactions between the cells causes the cytotoxic T cell to leave the normal cell alone.
Cancerous cells are not so lucky. The DNA in these cells is often heavily damaged, and as a result, improperly-formed MHC I cells are often present on the surface. When a cytotoxic T cell interacts with these malformed proteins, it recognizes that something is wrong and triggers a chemical process that ultimately kills the cancer cell.
Some cancer cells can actually evolve to not express MHC I proteins at all! In this case, the cytotoxic T cell cannot interact with the cancer cell and kill it. However, the NK cell is the "backup" option for this problem. NK cells will scan the cancer cell, and the lack of MHC I proteins on the cancer cell's surface will activate the NK cell. This leads to the death of the cancer cell.
I apologize for the long explanation, but immunology is an incredibly complex subject! Hope this helps!
~AP
