Hi guys, this is Dr A so next in our basics of the lab series we are going to introduce immunohematology so what is immunohematology? it's the study of the immunological response to blood components, blood banking more specifically are the procedures involved in the collection storage, and processing of blood, and the distribution of packed red blood cells and blood components so blood banking is involved in you donating blood and it getting processed and distributed to the local hospitals that need it; transfusion medicine happens at the hospital and it's the medical practice and techniques associated with the replacement of red cells and blood components so it has to do with then giving those donated units to the patients but first making sure that they've been appropriately matched so that the unit is helpful and not harmful to the patient; so a unit of donated whole blood can be separated into a variety of blood components and derivatives which allows it to be used for a number of therapeutic purposes so some of the examples of blood components and derivatives include, other than red cells, packed cells, which what we really think of when we think of blood donations, we think of the red cells, but there's also fresh frozen plasma, which is what's represented here in this picture there is also cryoprecipitate, so cryoprecipitates are in a much, much, much smaller bag than the frozen fresh frozen plasma, platelets, platelets are going to be in a bag that's bigger than that of the fresh frozen plasma but platelets are not frozen, they're going to be at room temperature and then uh factor eight concentrate and that's again going to be in a much much smaller container so accuracy is always important in the lab but it is absolutely essential in transfusion medicine so even the smallest error can directly result in the death of a patient from a hemolytic transfusion reaction, so this is so scary because this is the one department in the lab when, if things are not done right, you can literally kill a patient, so as R.R Race said "blood group tests are different from most laboratory tests used in medicine in a vital way, the reported test must be correct for the wisest physician cannot protect his patient from the consequences of a blood grouping error" and so this, you know, starts with proper identification of the patient at the time of the sample collection and proper labeling, etc. of the samples that are collected to be used to type the patient, to match them to the units that you know might be given but it's also picking up the right unit, identifying the... labeling those units properly and then when the nursing staff comes and gets those units, make sure that they're picking up on the right patient and then when they get to the floor they're actually giving it to the right patient, so things can go wrong in so many ways but if at the beginning the wrong patient is stuck for the sample, and mislabeled, then it can have really disastrous consequences down the line, let's talk about the concepts of antigens and antibodies, so the primary immunology components that are involved in blood banking and transfusion medicine are antigens and antibodies, so an antigen is any substance that's capable of inducing antibody formation and those antigens can be things like viruses, bacteria, which is kind of more representative of the little green dots here in this picture, whereas with the blue Ys are the antibodies, so little free-floating viruses and bacteria there could also be things like if you have a food sensitivity like I do, it could be to gluten or gliadin or it could be to molecules of casein in dairy and stuff, and cause reactions so um you know if you can make an antibody to it then it's an antigen an antibody is a protein also known as an immunoglobulin that is produced in response to a foreign substance or an antigen now most foreign substances are antigenic but not all antigens are foreign substance so a foreign substance would be a pathogen entering your body so a pathogenic bacteria or virus, or something like that but there are things, like you can make antibodies to your own tissue, and that would be the whole realm of autoimmune diseases where your body is kind of turning against itself and you make an antibody to thyroid tissue in Hashimoto's for example and so you know those antigens are not foreign but you have a misguided immune response to it okay so within an antigen it's also important to know that there are several epitopes, so an antigen is usually a molecule and that molecule is often on the surface of a cell or you know it could be a spike on a virus again something part of the cell membrane of the bacteria something part of a cell membrane in the body and that molecule has a certain shape and antibodies could attach to different areas of that molecul,e and each area it could attach to on that molecule is considered (and called) an epitope, and um they are different, okay, and so um you can make several different antibodies, if you will, to the same antigen but simply they're there to different epitopes on that antigen, and so um you know these could be, um let's say this could be a molecule of gluten, or something like that, well um you know they could make antibodies to this epitope, that one, or that one and then this antibody that has uh the triangle shape fitting the triangle epitope would not react to the circle shape and it would not react with the rectangle shape, and so they're very specific and they fit, so each antibody is, kind of has this Y shaped tail and then two little arms, right, little hands and the ends of the arms here are what latches on to the epitopes and they're specifically made to fit exactly that epitope and nothing else, okay, so um sometimes that's why like in testing, we make, if if the antibody for testing is only to one epitope and for some reason it's not reacting, or that the antigen that you're testing doesn't have that epitope, then you could get a negative reaction when the antigen is actually still there, so that's getting a little bit deep there, but um just know that antibodies have variable regions and those variable regions are made to attach to the epitopes, which are areas on the surface of an antigen and an antigen is a usually a pretty big molecule so molecules that are antigenics are are bigger molecules such as proteins, proteins are very antigenic so um each species of animals, including humans has certain antigens that are unique to that species and they're usually present on the red cell membranes of the members of that species, so on the surface of red cells of humans are antigens that says "Hey! I'm a human red cell" and if you were to get blood from a dog and try to transfuse it in a human then you, there would be a reaction because it's seeing the antigens on the surface of the dog's blood as dog, right, and so um those interspecies things (mismatches) can cause big reactions and um so and this is not just for red cells, this is for all the cells in your body um you have cells, you know, they have markers on the cells that say "I'm human" and then you have markers on the (body) cells that say that these belong specifically to you, okay, so they can say hey I belong to Mike! I belong to Emily! I belong to Dominique! or whatever, okay and um so that gives you know kind of a unique fingerprint of antigens for each person, even within members of the same species, so within humans, there can be antigens that are found on the surface of red blood cells of some, that are not found on the red blood cells of others, and there are some antigens that are more common than others, so the ones that are the most common are the A and B antigens in the ABO system and Rh antigens which are actually D, E and C antigens, and little d, little e, little c antigens in the Rh system but there are other systems of antigens such as like Kell, and Duffy, and Lewis, and... see there are so many of them, they can be there's quite a unique combination on every person, and so it's.. we definitely have to identify the most prevalent ones, the most common ones, but then sometimes, if a person is getting a lot of transfusions, that we have to get down to the nitty-gritty and match them to a deeper level of the antigens so if blood contains a foreign antigen on the surface of the red blood cell and it is transfused into your recipient whose blood cells do not have that antigen, this recipient then can form antibodies to that particular antigen and this is because you only make antibodies to antigens things that you don't have, you've never seen before, okay so, if you have it, you're just not going to make antibodies to it, we can use the Rh system to explain that so if you are Rh-positive, and you have the Rh antigen on the surface of your red cells, and you're given Rh-positive blood there's not going to be any problems because you you already have that antigen and your body knows what it is, it's fine, it's not going to react, but if you were Rh-negative and due to some traumatic circumstances you are given Rh-positive blood to save your life right, well, and if you're Rh-negative you, and you've never gotten Rh-positive blood, or never encountered Rh-positive antigen, you won't have any antibodies, so as soon as you start getting that Rh-positive blood, your body is going to be like what's this? and it's going to start mounting antibodies against that Rh antigen because you've never seen it before, you don't have it and then from then on out, for the rest of your life, you will have anti-Rh also known as anti-D antibodies, and you will never be able to get any more Rh pos blood ever again, less you have a massive transfusion reaction, so once these antibodies are present in the recipient's plasma, future transfusions of red cells that have that antigen can cause a significant and possibly life-threatening adverse immune response or a transfusion reaction, and so from then on out, let's say the antibody is not an Rh antibody, maybe the antibody is one of the Kell antibodies, then you have to make sure, from there on out, that they get blood, anytime they have to get blood, that blood will have to be screened and be negative for that antigen and we check for the presence of these antibodies beyond just ABOand Rh anytime a cross-match, or an order for blood matching has been put into the system for a patient, so transfusion reactions are very important to identify, so the symptoms, which can vary from patient to patient, can include chills, fever, low back pain, or flank pain, nausea, vomiting, and then shock, which is going to be evidenced by a decreased blood pressure and a rapid pulse, and you will see that those are two measures that are often taken during the the beginning of a transfusion of a blood product, the nurse is supposed to check their blood pressure, usually every 15 minutes or so and along with that check their pulse and be looking for any changes and obviously what we're looking for is the pulse going up and the blood pressure dropping, all right so that wraps up this introduction to immunohematology, I'll see you in the next video!