Blood Groups

Prof. K. Sivapalan

June 2013 Blood grouping 2

Blood groups.

• Transfusion reactions indicated different types of blood among individuals.

• Surface antigens on red cells are responsible for the differences.

ABO system.Rh system.MNSs, Lutheran, Kell, Kidd, ….over 500.Inheritance and expression differ.

June 2013 Blood grouping 3

ABO system.

• H antigen is a oligosaccaride with galactose and fucose at the end. [present in all persons]

• N-acetylgalactosamine added to galactose – A antigen.

• Galactose added to galactose – B antigen.

• A1 – 1,000,000 in one RBC.

• A2 – 250,000 in one RBC.

June 2013 Blood grouping 4

ABO groups.

Presence of,H and A antigens→ blood group A.H and B antigens → blood group B.H, A and B antigens → blood group AB.H only → blood group O

June 2013 Blood grouping 5

Production of antibodies.

• Antigen present at birth is recognized as self [clone deletion]. It is found in salivary glands, pancreas, kidney, liver, lungs, testes and semen.

• Therefore, no antibodies for H antigen.• If A antigen is absent, anti A is produced after exposure.• If B antigen is absent, anti B is produced after exposure.• A and B antigens are seen in bacteria that colonize colon

and lead to production of anti bodies for absent antigens in the blood.

• The antibody is IgM.

June 2013 Blood grouping 6

Genetics of ABO.

• Genes are Mendalian allelomorphs.Phenotype: O A B AB

Genotype: OO AA AO BB BO AB

Incidence: O – 60 %, B – 20%, A – 15%, AB – 5%.

Medico legal: exclude father.

June 2013 Blood grouping 7

Blood grouping.

• Take one drop of antiserum.

• Add one drop of red cell suspension.

• Mix gently.• Agglutination

indicates the group.• [agglutinogens and

agglutinins]

June 2013 Blood grouping 8

Rh group.

• Studied first in Rhesus Monkey.• Has not been identified in tissues other than red

cells.• C, D, E and other antigens are identified but D is

the most antigenic.• If red cells agglutinate with anti D, the blood is

Rh positive otherwise negative.• Rh –ive person will produce anti D only when

exposed to Rh +ive red cells.• The antibody is IgG type.• About 85 % of the population is Rh +ive.

June 2013 Blood grouping 9

Rh group and pregnancy.• Rh –ive person will produce anti

Rh after exposure to D antigen.• Foetal blood can enter maternal

blood at separation of placenta.• If mother is Rh –ive and the

baby is Rh +ive, mother can start producing anti D.

• Anti D, IgG, can cross placenta. It will react with foetal RBC.

• Rh –ive mothers should be given anti D injection immediately after partus of each Rh +ive baby.

June 2013 Blood grouping 10

Blood transfusion.

• Blood is transfused to patients in acute loss of blood – hemorrhage.

• Packed cells are transfused in severe anemia.• Fresh blood is given to replace deficient clotting

factors [ now purified products available].• Incompatibility will cause antigen – antibody

reaction.• Main problem is red cell antigens [blood groups]

but other materials in donated blood also can cause reactions.

June 2013 Blood grouping 11

Precautions for transfusion.

• Grouping for ABO and Rh groups.• Direct testing of donor and recipient blood.

– Donor RBC + receiver serum.– Donor serum + receiver RBC.

• Main problem is the antibody in the recipient blood destroying donated RBC.

• In large amounts, donor antibodies can react with receiver RBC.

• Never give Rh +ive to –ive.• Screen for infections- AIDS, Hepatitis, Malaria,

Typhoid etc.• Autologous transfusion

June 2013 Blood grouping 12

Blood bank.

• Storage of blood:– 4˚C for 21 – 35 days. [citrate and dextrose]– Deep freezer for 6 – 12 months.– Loss of granulocytes and platelets.

• Precautions on collection of blood.– Sp. Gravity- avoiod anaemic blood.– Screen for infections- AIDS, Malaria,

Hepatitis, etc.• Autologus transfusion. [safest].

June 2013 Blood grouping 13

Transfusion reactions.

• Haemolysis – incompatibility.– Haemoglobinurea, renal failure.– Dyspnoea, chest pain, chills, fever, renal insufficiency,

death.• Acute hyper volumic effects.

– Acute Cardiac failure, hypertension.• Reaction to white cells, platelets, plasma

proteins.• Pyrogenic reactions.• Hypocalcaemia.• Hyperkaelaemia.

HLA Antigens

• Six of these antigens are present on the tissue cell membranes of each person

• There are about 150 different HLA antigens to choose from.

• Therefore, this represents more than a trillion possible combinations.

• Tissue typing for these antigens is done on the membranes of lymphocytes

• Some of the HLA antigens are not severely antigenic so, a precise match of some antigens is not always essential to allow allograft acceptance.

June 2013 Blood grouping 14

Tissue Transplantation• When organs are damaged by disease, transplants are

attempted.• Transplanted tissue may be attacked by antibodies

produced against antigens in the transplant.• It does not occur when it is autograft or isograft (identical

twin)• Tissues from others will have antigens against which

antibodies can be produced in 1-1 day to 5 weeks after transplantation unless Specific therapy is used to prevent the immune reactions.

• With proper “matching” of tissues many kidney allografts have been successful for at least 5 to 15 years.

June 2013 Blood grouping 15

Prevention of Graft Rejection

• Glucocorticoid hormones• Drugs that have toxic effect on the

lymphoid system• Cyclosporine, which has a specific

inhibitory effect on the formation of helper T cells

• Danger: bacterial and viral infections can become rampant

June 2013 Blood grouping 16