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Blood Groups. DIFFERENT BLOOD GROUPS. ABO system. The membrane of RBCs contain antigens of two types (A) and (B) Characters of these antigens are : - inherited according to Mendelian law - appear in fetal life and persist throughout life.

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Blood Groups

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Blood groups

Blood Groups

Different blood groups


Abo system

ABO system

The membrane of RBCs contain antigens of two types (A) and (B)

Characters of these antigens are :

- inherited according to Mendelian law

- appear in fetal life and persist throughout life.

- specific reaction with the corresponding antibodies

In the plasma there are antibodies against A and against B and they also are inherited.

According to the types of antigens and antibodies the blood groups are classified into

According to the types of antigens and antibodies, the blood groups are classified into:

Blood groups

universal recipients

universal donors

Importance of blood groups

Importance of blood groups

In disputed paternity (good negative test).

In the criminal practice.

(1) Medicolegal importance:

(2) Blood transfusion

The recipient’s plasma should not contain

antibodies against the donor’s red cells

Incompatible blood transfusion

Incompatible blood transfusion

  • The donor’s RBCs are agglutinated by recipient plasma

  • The donor’s serum are diluted by recipient blood so its antibodies are with less or no effect on the recipient RBCs

Rhesus monkeys


Rhesus factor rh factor

Rhesus factor (Rh-factor)

People are divided according to the presence or absence of Rh- antigen (agglutinogen) on RBCs membrane into:

Rh +ve (have D- antigen) = 85%

Rh –ve (without D- antigen) =15%.

Rh antibodies


They differ from ABO antibodies in:

1- They are normally absent

but induced by blood transfusion of Rh positive blood to Rh-negative patient

or in pregnancy.

Blood groups

2- Rh-antibodies are IgG but ABO-antibodies are IgM .

- IgM has large molecules and can’t cross placenta

- IgG has small molecules and can cross placenta.

Importance of rh factor

Importance of Rh-factor

A- Erythroblastosis fetalis

Rh +ve male + Rh –ve female

 Rh +ve fetus

Rh +ve fetal RBCs enter the circulation of the mother and sensitize her liver to produce anti- D antibodies (agglutinins).

Blood groups

- Antibodies (IgG) cross the placenta to the Rh +ve 2nd fetus

- The 2nd or 3rd fetus is born anaemic, jaundiced or born dead

- The 1st baby is also affected if the mother is sensitized by previous transfusion of Rh +ve blood.



1- Rh –ve female should never receive Rh +ve blood

2- Anti-D antibodies are given to the mother during 48 hours after each delivery to neutralize the D-antigen of fetal RBCs transmitted to her  prevent formation of liver antibodies


Gradual replacement of baby’s blood with Rh –ve group O (exchange blood transfusion).

Blood groups

B- Repeated blood transfusion:

If Rh –ve person is transfused with Rh +ve blood he will produce antibodies against Rh-factor

if this person retransfused with Rh + ve blood  agglutination

Blood groups

Determination of blood group:

1- By slide technique

2 by cross matching between recipient and donor blood

2-By cross matching between recipient and donor blood

Group A + Group B = Clumping of RBCs


Blood transfusion

Blood Transfusion



1) Decrease blood volume (haemorrhage more than 30%).

2) In severe anaemia (Hb is less than 7gm/dl).

3) Restore blood contents as platelets,packed RBCs or clotting factor as in purpura and hemophilia

4) Erythroblastosis fetalis by exchange transfusion.



1) Blood is obtained from healthy donors

- Age =18-60 year

- Weight: more than 55 kgm

- Blood pressure within normal range

- Hb% is not less than 90% (13gm/dl).

- Haematocrit value at least 40%.

- Free from infectious diseases as AIDS, viral hepatitis

Blood groups

2) Blood used is stored at 4C not more than 21 days

3) Blood bag must contain, sodium citrate (anti-coagulant), citric acid (reduce pH) and dextrose (nutrient of RBCs) .

4) Blood groups are compatible by double cross matching test

5) The blood is warmed before transfusion to restore the Na-K pump

Complications of blood transfusion

Complications of blood transfusion

A- Incompatibility whichleads to:

1. RBCs are agglutinated in clumps 

block small blood vessels  pain in chest and back

2. Agglutinated RBCs hemolyse and hemoglobin is liberated in plasma and Converted to bilirubin  post-transfusion jaundice and precipitated in renal tubules blocking it  renal failure .

B other complications

B- Other complications

1-Transmission of diseases as AIDS & hepatitis B,C.

2- Excessive transfusion  heart failure.

3- Hyperkalemia  arrhythmia

4- Hypocalcemia  tetany

5- Allergic reactions

Changes occur in stored blood

Changes occur in storedblood

1- Increase K+ ions in plasma (Na-K pump inhibited by cold) .

2- Decrease dextrose and changed to lactic acid.

3- Decrease Platelets number .

4- RBCs swell and become spherical.

5- Decrease clotting factors VII, VIII , IX

6- Decrease 2,3 DPG  less O2 supply to the patient  hypoxia.

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