What is a “foreign body giant cell reaction”, and how do they happen?
In: Biology
Your immune system is involved to stop foreign/unknown things from getting into your body and harming you. One of the types of cells that do this are called macrophages (literally “big eaters”), which basically eat bacteria, viruses, etc in order to get rid of them.
Larger foreign bodies (like multi-cell parasites, or implanted materials) can’t be eaten by a single macrophage. Instead, a large number of macrophages cover the foreign body, and they all fuse into a giant cell. This giant cell then in turn forms a barrier that protects the rest of the body from whatever entered it.
Our immune system recognizes the cells in our body using special “flags” (on each cell which labels them as being friendly. Our blood type is a common example of these flags, but most of our cells have something different called an MHC which works the same way.
Intruders in our body like bacteria don’t have flags which our immune system recognizes, so the immune system tries to destroy those intruders. Our immune system can’t destroy larger intruders like implants, especially materials like metal, so the foreign body giant cell reaction is activated instead. The reaction activates a specific type of immune cell called macrophages, which will fuse to each other and form a giant barrier which eventually surrounds the object and isolates it from the rest of our body. This way the body isolates the object from possibly harming it, and the immune system doesn’t get constantly distracted by a large object that doesn’t have any flags the body recognizes. Our “flags” are genetic and can’t be changed, which is why the body doesn’t just accept the presence of the large object.
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