BLOOD GROUPS Blood groups are classified according to

BLOOD GROUPS § Blood groups are classified according to antigens on the membrane of RBCs called “Agglutinogen”, which are glycoprotein. § The plasma may contain antibodies called agglutinins. § Two main systems of antigens and hence grouping are the ABO and Rh systems.

ABO system § 1 - Group (A): 40% of population, RBCs has A Agglutinogens and the plasma contains anti B antibodies. It may be homozygous (AA) or heterozygous (AO). § 2 - Group (B): 10% of population, RBCs have B antigen and plasma contain anti A it may be homozygous (BB) or heterozygous (BO).

ABO system to be continued § 3 - Group (AB): 5% of population, RBCs has both agglutinogens A + B, the plasma does not contain agglutinins. § 4 - Group (O): 45% of population, RBCs has no agglutinogens, but the plasma contains both agglutinins Anti A + Anti B.

Rh System § People are classified according to the presence or absence of Rhesus antigens (most common type D) into Rh+ve with D antigen 85% and Rh-ve without D antigen 15%.

Importance of Blood Groups: 1 -Medicolegal importance: Disputed parenthood. Regarding blood group inheritance 2 antigens are inherited from both father and mother. These antigens determine the group. The A + B antigens are dominant while the O one is recessive. § In group A (phenotype A) the genotype may be AA or AO. § In Group B may be (BB or BO). § In Group AB and O (AB or O). § Blood grouping is a good -ve test in disputed parenthood

2 - Blood Transfusion § If transfused blood is incompatible usually the donor RBCs are agglutinated by recipient plasma as the donor’s serum is diluted in recipient blood. - Group O: is the universal donor (no agglutinogens). - Group AB: is the universal recipient (no agglutinins).

3 -). Importance of Rh factor: (Erythroblastosis Fetalis) § The disease occurs when an Rhve mother carries an Rh+ve fetus, small amounts of fetal blood leak into the maternal circulation at the time of delivery, thus the mother will produce Anti D agglutinins.

(Erythroblastosis Fetalis) to be cont. § During the next pregnancy the mother agglutinins cross the placenta (Ig. G) to an Rh+ve fetus causing hemolysis of fetal RBCs and may lead to: § Anemia of fetus § Death of fetus. § Jaundice with deposition of bile pigment in the basal ganglia (kernicterus syndrome) as the blood brain barrier is not developed yet (Erythroblastosis Fetalis).

(Erythroblastosis Fetalis) to be cont. § The first baby (Rh+ve) is affected in case of maternal sensitization by: -Previous Rh +ve blood transfusion. - If the baby was born alive should be treated by exchange blood transfusion with Rh -ve group O blood.

(Erythroblastosis Fetalis) to be cont. § Fetal-Maternal hemorrhage during pregnancy. § This disease can be prevented by avoiding Rh+ve blood transfusion to Rh-ve females, and if pregnancy and labor happened an anti -D antibodies are given to neutralize the D antigens of the Rh +ve fetal cells and prevent sensitization of the mother.

BLOOD TRANSFUSION § § § § Indications If the whole blood or any of its components is deficient blood transfusion is indicated as in case of; - Acute hemorrhage. - Severe anemia. - Agranulocytosis. - Thrombocytopenia. - Hemophilia. However, if one element only is deficient it is preferable to give this particular element e. g. packed RBCs and human plasma transfusions.

Precautions § - Blood should be compatible (ABO and Rh) assured by cross matching test. § - Blood should be free from contamination. § - Blood should be free from blood born diseases. § - Blood should be fresh (less than 2 weeks storage). § - High hemoglobin content.

Precautions to be cont. § Blood is stored at 4 o. C and added to: - Sodium citrate as an anticoagulant. - Dextrose as a nutrient for cells. - Citric acid to reduce the p. H. - Storage lead to decrease in platelets, coagulation factors VII, VIII, IX and dextrose, while there is increase in lactic acid content, K and haemoglobin released from haemolysed RBCs.

Complications § The donor may suffer from anemia in repeated donation and shock in excessive volume donation. The recipient may suffer from: § 1 - Mechanical effect: - Air or fat embolism. - Dislodgement of a thrombus. § 2 - Infective complications: E. g. infective hepatitis, AIDS or Malaria. § 3 - Physiological complications: - Overloading in excessive transfusion leading to heart failure. - Pyrogenic reaction i. e. fevers.

§ 4 - Incompatibility complications § Agglutinated RBCs may block small vessels causing severe pain, or haemolysis follows i. e. , liberation of hemoglobin, K+ and toxins into plasma. a) Hemoglobin liberation will cause: - increased blood viscosity leading to heart failure. - conversion into bile causing jaundice. - precipitate in renal tubules as acid haematin causing renal failure. - hypoxia. § b) K+ causes arrhythmia. § c) Toxic substances cause powerful vasoconstriction of renal vessels causing acute renal failure.