 In ABO blood grouping, you know there are two types of antigens on the surface of RBCs, the A antigen and the B antigen. And depending on the presence or the absence of the antigens, the blood types AB, AB and O are determined. How? If the red blood cells of a person have only the A antigen, then the person is said to have blood group A. If they have only the B antigen, then the blood group is B. If the red blood cells have both A and B antigens, the blood group is said to be AB. And if the red blood cells of a person have neither A nor B antigens, then the blood group is supposed to be O. But when you get your blood typing done, what do you see on your report? You see something like AB positive or B negative or O negative. So where are these positives and negatives coming from? That is what we are going to learn about in this video. So besides the A and B antigens, there is another antigen that is found on the surface of RBCs. It is called the RH antigen or the RH factor. The RH is named after the Rhesus monkeys on which these experiments were first performed. So some people, they have this antigen on their RBC surfaces and these people are said to be RH positive. And the people who do not have this antigen on the surface of their RBCs, they are called RH negative. So the pluses and minuses that you see on your blood reports besides AB and O are nothing but this RH factor, the presence or absence of it on your RBCs. So let's look at the compatibilities. Which type of blood can be donated to who? So what if there is an RH positive blood that is donated to an RH positive person? What do you think will happen? The RH positive blood has the RH antigen on its RBCs but so does, so do the RBCs of this person. This person has the RH antigen too. So they are a match, so they are compatible. So yes, RH positive blood can be donated to an RH positive person. What if we try to donate an RH negative blood to an RH negative person? Again, the same thing. It's a match, so there is no problem, right? What if you try to donate RH negative blood to an RH positive person? Now let's remember what an RH negative blood has. It has nothing. It doesn't have the RH antigen on the RBC surfaces. But the RH positive person does have the antigen. So is there an incompatibility? No, because there are no antigens in the blood that is being donated. So the person will not produce any antibodies. So he's safe. He's fine. Now let's look at the last case where RH positive blood is donated to an RH negative person. The RH positive blood has the RH antigens. So what will the blood of the RH negative person do? It sees the RH antigen and recognizes it as foreign because he himself does not have that antigen. So what he'll do is he will produce antibodies against the RH antigen. And what happens then? The antibody will react with the RH antigen and there will be blood clotting and then severe reactions and that's not good for the person at all. So RH positive being donated to an RH negative person is an incompatibility. Now let's look at a special case of RH incompatibility. Let's say a woman who is RH negative is pregnant with a child who is RH positive. How does that happen if the father of the child also happens to be RH positive then this kind of a situation can arise. So what do you think will happen? During the first pregnancy what happens? So the placenta is arranged in such a way that the blood of the mother and the child is not supposed to mix. So in the first pregnancy it's fine even if the blood types are incompatible everything goes fine. However when the woman gives birth to the RH positive child a birth can often be a messy affair and what happens is her blood may get exposed to the blood of her child a little bit and when that happens her blood immediately recognizes the RH antigen as a foreign particle and immediately her blood starts making antibodies. So now let's see what will happen when she gets pregnant with an RH positive child again. So this is the second pregnancy and again she's negative and the child is RH positive but the last time she was pregnant with RH positive child she got exposed to the blood of the child a little bit during birth of the child and so now she has antibodies. She has these antibodies and what do you think these antibodies will do? They will attack unfortunately they will attack the RH antigen of the child and then what will happen? Worst cases it can be fatal to the child and if not the child anyway can be born with anemia and jaundice and this condition is called erythroblastosis fetalis but don't worry these days we have a cure for it. What is the cure? So you see these antibodies right the antibodies which were so deadly for the child nowadays we have antibodies available to these antibodies. So there are these antibodies which can recognize the anti RH antibodies of the mother and it is these antibodies which when injected to the mother will destroy those pink antibodies that you see the anti RH antibodies and the child will be fine. So taking into consideration both the A and B antigens and the RH antigen these are the different blood types that we can have O negative O positive A negative A positive and so on and when we look at the compatibilities whether a particular blood type can be donated to a particular person we have to consider the A and B antigens as well as the RH antigen. So now we have this table where these are the different types of donors and we have the different types of recipients. Can you fill the table saying which combinations are compatible and which combinations are not? So let's look at some of them. So here we have O negative donor and O negative recipient. So what antigens do they have? The donor so O negative blood it has none of the antigens A or B or RH factor so that means no antibody production so this is compatible. What about O negative and O positive? Now the O blood group means neither A or B antigen is present but the RH factor is present in the O positive blood group right but this is the blood group of the recipient so the recipient the person who will receive the blood he will have the antigen the RH antigen and the donor blood will not have the antigen because that's negative so the recipient blood has nothing to produce antibodies again so again this is compatible. Now let's look at the opposite what if O positive blood is donated to an O negative person if O positive is the donor that blood will have the RH antigen and O negative if that's the recipient then the recipient will not have the antigen so the recipient's body will produce antibodies against the donor blood and this is not compatible. So can you work out the rest of the table? Take some time pause this video and figure out which is compatible which donor blood can be donated to which recipient. So here I filled out the first column for you here the O negative is the donor blood and all the others are recipients now O negative has no antigen whatsoever right so no matter who it is donated to it will always be compatible because the recipient will not produce any antibodies because there are no antigens to produce antibodies against so O negative is called the universal donor. Similarly if you just consider the AB positive as the recipient AB positive means what the recipient will have the A antigen the B antigen and the RH antigen so all the antigens are there so there is no way the recipient's body is going to produce antibodies against all these blood groups so no matter what donor blood is donated to the recipient AB positive it will always be compatible hence the AB positive blood group is called universal recipient. How do you do the rest of it? Let's take the first row see the recipient is O negative that means they have no antigen so no matter what antigen is thrown at them there will be a reaction and there will be incompatibility of course O negative it was it was fine because it was a match but all the rest of them they have some or the other antigen and hence the O negative recipient will produce some or the other antibody hence none of these matches are compatible. Now let's take one more row let's take this row of A positive recipient let's consider the donors one by one O positive no A or B antigen but there is an RH antigen but A positive recipient also has an RH antigen so yes this is a compatibility A negative donor and A positive donor A negative does not have the recess antigen but it does have the A antigen the recipient also has the A antigen and it has the recess antigen so no problem so it's a compatibility A positive and A positive are of course compatible what about B negative donor and A positive recipient since it's RH negative RH factor wise the recipient is fine however since there is a B antigen in the donor but no B antigen in the recipient the recipient's blood will produce the antibody to the B antigen and hence this is an incompatibility similarly B positive donor is an incompatibility AB negative again it has the B antigen so it is incompatible A B positive is also incompatible so you can work out the rest of the table following this very simple principle whatever antigen the donor has if the recipient does not have the same antigen the blood will violently react to the donor blood and there will be an incompatibility otherwise it'll be fine so again take some minutes and try to complete the table by yourself okay this is the completed table of the donor recipient compatibility between the different blood groups which includes the A and the B antigens and the RH factor