so we're going to talk about the second line of defense and this is what we're going to use when that first line of defense gets breached you have a cut you have a scrape something and now pathogens are getting into your body okay so our second line of defense consists of antimicrobial proteins it consists of specialized cells and then some specific i'm just going to say process these okay so uh let's talk first about the antimicrobial proteins all right we have three different antimicrobial proteins that are going to help us the first one is called transferring and we know about transferrin because of um from from blood when the chapter on blood uh remember that um when the iron when hemoglobin breaks down red blood cell is no longer good anymore and it's removed by fixed macrophages in the spleen and the liver the heme the hemoglobin is broken down the globin is broken down into amino acids the heme is then going to the pigment portion is going to be broken down into other pigments that are going to be used for um eliminated through our urinary and digestive systems and then the iron is going to be going to be safe because iron is valuable okay we need it to make new hemoglobin so it's attached to transferrin travels through your blood goes to the site of red blood cell synthesis in the it can be stored in the liver or it can go to the bone marrow and once it does then it becomes ferritin it's attached to a protein and it's ferritin so transferrin is how it travels through your blood so as long as iron is attached to transferrin it's not available for pathogens to use for their own metabolism so some pathogens some bacteria require iron well if all your iron is tied up and they can't get to it it's going to be it's going to help um help prevent them from being able to to grow and flourish okay if they can't get iron and they need iron so transferrin is the first guy but we already know about transfer oh i'm going to get rid of that okay there we go the second one is something called interferon and you may have heard of interferon all right there's different kinds of interferon there's alpha beta and so forth and we're not going to go into it in any detail but um interferon so for those of you that haven't had micro let me just give you a little quick and dirty uh viral 101 okay so here we have our cell and here's our virus virus infects the cell the virus takes over the nucleus and turns the nucleus into a virus-making factory it turns a cell into a virus-making factory because viruses aren't considered to be living right they are um sort of the innate they they they don't have their own metabolism they cannot um replicate without a host they have to have a host because they don't have the capacity to make more of themselves outside of a host so they infect cells specific kinds of cells take them over turn them into virus-making factories and then the cell dies from a number of different reasons first thing might be because uh it's so busy making viral particles it doesn't have time to make its own okay so we have two basic kinds of viruses we have ones called lytic viruses and those are viruses where this entire cell is going to fill up with virus until it pops open and releases the viral particles so the cell becomes so huge and swollen with viral particles and then it pops and releases all those viral particles and of course the cell is dead it's going through lysis all right the other kind is um budding viruses and there you have again it's turning it into a virus making factory but it's sort of like the viral particles are leaving sort of like through exocytosis they're taking a little bit of the cell membrane with them and they've caused different proteins to be put into the cell membrane so they have this lipid bilayer with proteins in it spikes in it and they bud off of cells okay but regardless of how the virus gets their the cell is gonna die the cell is eventually going to die too right because it's it's too sick it can't make it it can't take care of itself anymore because it's too busy making viruses all right so how does interferon work okay so here we have our cell and the cell is infected with virus and it releases some viral particles now here is the neighboring cell that guy's not infected yet once this cell gets infected it releases interferon and interferon is kind of like an altruistic type of thing meaning that it's this said this cell here is going to be dead there's no saving him okay but by releasing interferon the cell next to him that isn't infected can take it up and it won't prevent this cell from becoming infected i'm going to rewrite that word it won't prevent infection it will interfere with viral replication okay so that when a virus then infects this cell it's not going to kill it it's not going to prevent the virus from being able to infect the cell virus can still infect the cell what it's going to prevent is that virus then from taking over the cellular machinery and turning it into a virus making factory now virus is just either you know dna or rna with a little bit of membrane around it and so if um the virus is in the cell and it can't make more of itself the cell can actually um it will degrade it will break down so interferon can is released by cells that are infected and it uh is taken up by neighboring cells to save their lives basically okay so it interferes with viral replication and interfere on okay um so that is just the basics of it all right there's a lot more to interferon than that and there's certainly a lot more to viral viruses and viral replication than that but just a quick and dirty background for you okay so the third thing then is the complement cascade complement proteins now complement is a series of it's more than 20 different proteins that are found these are plasma proteins that are found in your blood and they enhance or complement other immune activities other immune what can i say other immune reactions other immune [Music] reactions sounds good okay and they operate as a cascade so what would that be well we looked at the blood clotting cascade one thing activates another thing activates another thing that's kind of how these guys work okay we're not going to focus on those because we're going to take the time that we have and spend most of it talking about b cells and t cells okay and i'll mention complement a little bit as we go along but it's not going to be a major focus so these are three different types of antimicrobial proteins that come into play if a pathogen breaches that initial barrier okay now the next guy the next thing is specialized cells and there's two different kinds of specialized cells that um two categories of specialized cells there are first of all the natural killer cells are nk cells and then the phagocytic cells and the phagocytic cells are the neutrophils and the macrophages eosinophils have a little bit of phagocytic ability but they wouldn't necessarily be classified as phagocytic cells okay um so natural killer cells natural killer cells are t cells uh they are they're not t cells sorry about that they are lymphocytes remember when we do that chart we have the different lineages and it was either a myeloid or lymphocytic lineage the lymphocytic it was b cells t cells and natural killer cells these make up a tiny tiny fraction of all lymphocytes these natural killer cells but they're really important these guys are constantly looking uh for any cell that does not have the right mhcs mhc stands for major histo compatibility complex histo tissue compatibility so tissue typing okay so major histocompatibility complex if sort of like your cellular dog tags my immune system needs to know what is me it needs to recognize self before it can um work properly okay it has to know what's me to know what's not me and so all of your cells except for the red blood cells have these little markers on them that say mine say heidi and so my immune system goes okay okay that's me that's me that's me that's not me i better kill it okay and so these are the reason why you have to take anti-rejection drugs if you have a transplant because your immune system is constantly looking for guys that don't belong and killing them and it will if you get a kidney transplant it will kill that kidney because they say whoa whoa this doesn't belong here it's foreign it could do us harm and i'm gonna kill it