BLOOD GROUPSThe outer layer of the red blood cell membrane contain certain antigens which are called agglutinogensBecause they cause red blood cell agglutination they are chemically glycolipidsAccording to the persence or absence of these agglutiogens in the red blood cells, individuals are divided into four major blood groups: A,B,AB OGroup A individuals contain agglutinogen AGroup B individual contain agglutinogen BGroup AB individuals contain both A and B agglutinogenIn the plasma there are two types of agglutinin (antibodies )Group AGroup A develop Beta agglutininBeta agglutinin in their plasma .Group BGroup B develop Alpha agglutininAlpha agglutinin in their plasma Group ABGroup AB don’t develop any agglutinin in their plasma.Group OGroup O develop both alpha and beta in their plasmaAs a general rule the blood of any person does not contain an agglutiinogen and its corresponding agglutinin I otherwise agglutinations and hemolysis occurs.

• When group A come in contact with plasma which contain alpha agglutinin they become sticky and clump and the hemolysis produce serious effect.

• Also agglutinogen occurs when group B red cell mix with plasma containing beta agglutinin.

• A persons whose group o whose plasma contains both alpha & beta agglutinin should not be given either groupA,B or AB and only his group O is given.

• A group O is called universal donor as it contain no agglutinogen in RBC and is not agglutinated by the membrane of any group.

• Group ABGroup AB is called universal recipient plasma has no agglutinin and can receive blood from all other group.

•

Erytheroblastosis foetalisErytheroblastosis foetalis• This is agglutinogen normally present in the red blood cell of rhesus

monkey• They are 6 varieties known as C,D,E ,c,d,e antigen (each is called RH

factor).• These antigens were also discovered in the human red cells particularly D,d

antigens and d has the strongest antigenic effect.• They are inherited from mother, father ,the D is the dominant and d is

recessive.So that genotype DD&Dd are RH+VE while genotype dd is RH-VE • Also 85% of population are RH+VE while 15% are Rh-ve.• But RH agglutinin are not naturally present. so the plasma of both RH+VE or

RH-ve person don’t normally contain antibodies to RH factor.• However the antibodies are formed only in the plasma of Rh-ve person if

they are transfused with RH+ve blood so the anti Rh antibodies will develop to his plasma

Importance & Dangers of RH antigen

• Transfusion reaction:• If Rh-ve individual recive Rh +ve blood he will develop Rh agglutinin in his

plasma ,and the second transfusion with RH+ve blood lead to agglutination and haemolysis of the transfused RBC.

• Erytheroblastosis foetalis;Erytheroblastosis foetalis;• This is a serious disease that can affect the Rh +ve fetus if his mother with

RH-ve and she was sensitized by Rh antigen ,in this case ,the formed RH agglutinins in mother plasma can diffuse across the placenta to the ,resulting in agglutination and haemolysis of his RBCs.

• The fetus will may die in the uterus or born with sever anemia (haemolytic jaundice) due to bilirubin formation.

• When the woman RH-ve marry man Rh+ve the fetus will be Rh +ve Like his fathe.

• Small amount of Fetal blood leak into the maternal circulation ,either during pregnancy through the placenta or at the time of delivery .

• Anti Rh agglutinin is formed during the next pregnancy agglutination cross the placenta to the fetus causing agglutination and haemolysis of its Rh+ve blood ,the fetus is usually born dead (Erytheroblastosis fetalis)

• The first infant can be saved because the amount of anti RH is not enough to kill the infant. this can be managed by rapid exchange of blood with groupO,RH –ve.

• Sometime erytheroblastosis f. can occur when a mother Rh-ve was previously injected with RH +ve blood ,the developed anti RH agglutinin cross the placenta to the fetus leading to destruction & haemolysis of its blood .

• About 55% of the RH+VE father are heterozygous (genotype Dd) So the fetes may be genotype dd (RH -ve )and mother sensitization don’t occur.

Ovoid and treatments of erytheroblastosis fetalis:

• RH-VE females should not transfused with RH +ve at any time even before pregnancy .

• If RH+ve mother delivers RH+VE baby ,she must given single dose of anti RH antibodies within 48h after labour ( which prevent formation of RH agglutinin in her plasma).

• On the other hand the erytheroblastosis baby can be treated by a repeated exchange blood transfusion with RH -ve during the first few weeks of life.

• About 400 ml of blood ,RH-VE blood are slowly infused at a time 1.5-2h while the baby blood is removed .as will as the RH agglutinin from the fetal blood and so keep the blood bilirubin low.