1. Blood Groups or Blood Types

2. The antigens on the surface of erythrocytes have been categorized into blood groups and more than 35 blood groups, most of which are rare, have been identified.
The ABO blood groups and Rh blood group are among the most important,and are much more likely to cause blood transfusion reactions. Other well known blood groups includes Lewis, Duffy, Kidd, Kell, Lutheran, and MNSs.

3. The ABO Blood Systems
The membrane of human red cells contains a variety of blood group antigens, which are also called agglutinogens.
The most important and best known of these are the A and B antigens. Because of the way these agglutinogens are inherited, people may have neither of them on their cells; they may have one of them or they may have both of them. In blood transfusion blood of Donors &Recipients are normally classified in toA,B,AB &O depending on the presence or absence of these antigens . When only A agglutinogen is present, the blood group is A; when B agglutinogen is present the blood group is B.

4. Agglutinins (antibodies)
If both agglutinogens are present the blood type is AB.If both agglutinogens are abscent the blood group is O .
If type A antigen is not present in a persons
red blood cells anti-Aagglutinins antibodies develop in the plasma,when type B antigens are not present in the red blood cells, antibodies known anti-B antibodies developed in the plasma;when both A & B antigens are present niether anti-A nor anti-B antibodies developed in the plasma;if both are not present both anti-A & anti-B antibodies developed in the plasma.

5. Genetic Determination of the Agglutinogens
Two genes determine the A,B &O blood types:
Genotype Blood type (phenotype)
OO O
AA or AO A
BB or BO B
AB AB
Some individuals with A agglutinogen is subdivided into type A1& A2 therefore there are 6 ABO groups:B,O,A1, A2, A1B& A2B .

6. Inheritance of A & B Antigens
The A1, A2, &B antigens inherited as Mendelian allelomorphs, A1,A2,and B being dominants. For example , an individual with type B blood may have inherited B antigen from each parent or a (B) antigen from one parent & an O from the other; thus the phenotype B may have the genotype BB homozygous or BO genotype (heterozygous) .
When the blood types of the parents are known ;the possible genotypes of the children can be stated.
When a blood types of a mother and her child are known ,it is possible to state whether a man with a given blood type could or could not have been the father. This is used for paternity.Typing can only prove that a man is not a father,but not that he is a father; with additional HLA typing DNA &other tests.

7. Four major blood types depending on the presence or absence of the A antigen, and B antigen
1. Type A. 2. Type B. 3.Type AB. 4. Type O.

8. Agglutinins (Antibodies): Antibodies against red cell agglutinogens are called agglutinins which are present in the plasma. The agglutinins are gamma globulins and they are produced by plasma cells(which are originated from plasmablast which come from activated (B-lymphocytes) system. Most of them are IgM (have 10 binding sites) and IgG (have two binding sites).

9. Table: blood groups their agglutinogens, agglutinins and % .
Universal donor 47
Anti-A, Anti-B - O 41
Anti-B A 9
Anti-A B
Universal recipient 3
A,B AB

10. ABO Transfusion Reactions Resulting from Mismatched Blood types Transfusion: If donor,s blood of one type is transfused in to a recipient who has a nother blood type,a transfusion reaction is likely to occur .
.Transfusion reaction or agglutination (clumping): is the reaction between agglutinogens in the donor's red blood cells and agglutinins in the recipient's plasma.{In very rare cases the RBCs of RECIPIENT are agglutinated by antibodies of the donor} because :1- plasma of the donor becomes diluted by the plasma of the recipient. 2- The plasma of the recipient (antibodies) react with the RBC of the donor(antigens) Dangerous hemolytic transfusion reaction occur when blood of the donor transfused into an individual with an incompatible blood type. The first problem is hemolysis of the agglutinated cells, hyperbilirubinemia, renal failure caused by :
1-Release of toxic substances from transfusion reaction 2- low RBC renal vasoconstriction low blood pressure circulatory shock urine out put decreases all these factors cause acute renal shutdown .

12. - + Type O Type AB Type B Type A Donor
Table: The compatibility & incompatibility between donors & recipients blood transfusion.
Donor
Type O
Type AB
Type B
Type A - +
Recipient

13. . The clumping of RBC is occurred by the following process: the binding sites of agglutinins can attach to more than two RBC’s at the same time there by causing the cells to adhere to each other. As a result clumping of RBC’s occurs. Then these clumps plug small blood vessels & hemolysis of cells occurs. Hb is liberated into the plasma & the level of bilirubin increases, finalyrenal damage with anuria cause death. So one of the most lethal effects of transfusion reaction is kidney shutdown and the person dies of renal failure