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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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.
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
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%.
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.
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.
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).
- 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).
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
Determination of blood group:
1- By slide technique
Group A + Group B = Clumping of RBCs
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
2) Blood used is stored at 4C 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
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 .
1-Transmission of diseases as AIDS & hepatitis B,C.
2- Excessive transfusion heart failure.
3- Hyperkalemia arrhythmia
4- Hypocalcemia tetany
5- Allergic reactions
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.