Mononuclear Phagocyte System (MPS) (Nursing)

00:00 So, the mononuclear phagocyte system, if you want to impress your friends at dinner, just drop that one on them and see what they know. We're going to talk about this network of cells that can do four of the following things. Right? So, #1, they can internalize or swallow up or digest large particles. To me, that always reminds me of Pac-Man. Now, these large particles could be anything from microbes, to dying cells, viruses, or even toxic compounds from metabolism. So, one of the 4 things that the mononuclear phagocyte system can do is internalize or swallow up and digest large particles that we want to get rid of. Now, the 2nd thing, they can present antigens. That means they can take these antigens and say "hello, immune system, this is what you need to recognize and get rid of." So they can swallow up large things and digest them. They can present antigens, foreign things that we don't want in our body to our adaptive immune system, so it'll remember these and not let them live again.

01:08 Third, it can secrete mediators. Now, mediators are kind of a weird thing. Chemokine and cytokine, they call migration and activation of immune and non-immune cells. That one we're not going to get really deep into, but we wanted to remind you that it does do that. Now, the 4th one, they actually have some cytotoxic activity. That means cyto- means cell, toxic means killer, so the mononuclear phagocyte system can also kill some cells which is pretty cool because in those cells that it can kill include some tumor cells and old and damaged cells. So, you can see the mononuclear phagocyte system is a pretty impressive network of cells that can do all four of these things. So, what are the cells of this incredible network? Well, the MPS includes 3 types of cells; monocytes, macrophages, and dendritic cells. Okay, so monocytes are the main type of mononuclear phagocytes in the blood. Mononuclear meaning 1 nucleus and they're in the blood. Macrophages are in the tissues. Remember, Kupffer cells. So, a really large percentage of the tissue-based macrophages are the Kupffer cells of the liver. So, we've talked about monocytes in the blood, the 1-nucleus phagocytes that are in your blood; macrophages that are in tissues, especially the Kupffer cells that we're focusing on; and the 3rd piece, the DCs share similar functional characteristics and are the most efficient of the antigen-presenting cells. So, of this mononuclear phagocytic system, we've got these 3 really important cells, monocytes in your blood; macrophages in your tissue, particularly the liver and the Kupffer cells; and DCs which are the most efficient of the antigen-presenting cells. So we looked at the 3 types of cells in the mononuclear phagocytic system. Why? Because we want you to understand the role of these cells in inflammation and fibrosis. See, when inflammation and fibrosis hit your liver, then that lobule is not going to be able to function very effectively, and the hepatocytes are going to struggle. So, we wanted you to understand it's a really important system but it can be very problematic for the liver as you head into liver disease, so inflammation and fibrosis is a type of stiffness and scarring within the liver. So, the mononuclear phagocytes and the Kupffer cells both play a role in that when the body gets kind of out of control when things go rogue. Now the mononuclear phagocytes, they're a key player of cellular immune defense, so we have to have them, but when things get out of balance, that's when we start to have damage to the kidneys. Kupffer cells are also phagocytic, it means it'll just kind of swallow up and to ingest, but they also produce a lot of substances and some of them are bioactive. They have a real impact on the body, so they play a role in inflammation and fibrosis. So, as we continue through this liver video series, it's important that you have just a basic understanding of the key players in that process.