Blood Groups: A Comprehensive Guide PDF

# Blood Groups ## Dr. Neven Makram Aziz ## Blood ABO system - Human blood can be classified into four major groups: A, B, AB, O. - The classification is based on the antigen nature of red blood cell membrane. - The membrane of red blood cells contains antigens called agglutinogen. - Plasma contain...

# Blood Groups ## Dr. Neven Makram Aziz ## Blood ABO system - Human blood can be classified into four major groups: A, B, AB, O. - The classification is based on the antigen nature of red blood cell membrane. - The membrane of red blood cells contains antigens called agglutinogen. - Plasma contains specific antibodies for red cells antigens called agglutinins (gamma globulin cannot cross placenta). - As a general role, blood of any person doesn't contain an agglutinogen (e.g A) and corresponding agglutinin (anti-A), otherwise agglutination will occur. ## Blood Groups: | Blood group | Red membrane agglutinogen | Plasma agglutinin | |---|---|---| | A (40% of population) | A | Anti-B (Beta) | | B (10% of population) | B | Anti-A (Alpha) | | AB (5% of population), universal recipient | AB | No agglutinin | | O (45% of population), universal donor | No agglutinogen | Anti-B and Anti-A agglutinins | - Agglutination of RBCs occurs between the agglutinogen of the donor's blood and agglutinins of the recipient's blood this is because agglutinin of the donor's: 1. Markedly diluted by the recipient's blood. 2. Markedly neutralized by free agglutinogen present in the recipient's blood (produced by the daily destruction of human RBCs). - The group O is called universal donors (this because RBCs of group O contains no agglutinogen and so no agglutination occurs when given) and the group AB also called universal recipient (no agglutinin in its plasma and so no agglutination occur). ## The Rh blood group system: - Rh factor: It is the agglutinogen which was discovered in RBCs OF Rhesus monkeys (hence the name). - It is present in 85% of people (called Rh positive "Rh +ve") and is absent in 15% of people (called Rh negative "Rh -ve"). - Normally, there is no anti-Rh antibody (incomplete IgG small enough to pass through placenta) in the blood in both Rh +ve and Rh -ve and it is formed only by two methods: 1. Blood transfusion from Rh +ve person to Rh -ve person. 2. Pregnancy of Rh -ve female by baby Rh +ve. ## Importance of Rh factor: 1. In blood transfusion; if Rh -ve person is transfused with Rh +ve blood, anti-Rh antibodies will develop in plasma but take time not spontaneous to reach maximum concentration so dangers (agglutination) will occur in second blood transfusion by similar group. 2. In marriage; if Rh -ve female married Rh +ve male, the fetus will be Rh +ve in most cases. - During delivery, Some fetal RBCs containing Rh agglutinogen may reach the mother's blood. - The mother will be developed the anti-Rh antibodies. - If this mother becomes pregnant again with Rh +ve fetus, the already formed antibodies cross the placenta to fetus and cause hemolysis of his RBCs. - If hemolysis is severe, the fetus may be death in uterus or may be developed anemia, jaundice due to excessive formation of bilirubin, which crosses the blood brain barrier of the fetus and deposited in the brain causing brain damage (Kernicterus). - This is called "Erythroblastosis fetalis" or hemolytic disease of the newly born. - The first baby may be also dying if the mother was previously transfused with Rh +ve blood and there is enough time (3-4 months) for formation antibodies. ## Prevention and treatment of Erythroblastosis fetalis - Preventing Rh -ve female from receiving Rh +ve blood (or marry an Rh +ve male as possible). But if this occurs: 1. Mother must be given a single dose of Rh immune globulin= anti-D antibodies within 48 hours to neutralize the antigens and inhibits the formation of anti-Rh antibodies. 2. Baby can be treated by repeated exchange blood transfusion with Rh-ve group O (determination of neonatal blood group is difficult) during the first weeks of life. - About 400 ml of Rh -ve group O blood is transfused over a period of two hours while the baby's blood is removed. - By time, transfused Rh -ve are replaced with baby own Rh positive cells. - A process that required 6 or more weeks so the anti-Rh (agglutinins} has come from the mother will been destroyed. ## Clinical significance: 1. It is important to know blood group in the following conditions: 1. Before blood transfusion to avoid incompatible blood transfusion and its complications. 2. Before marriage and during pregnancy to avoid erythroblastosis fetalis. 3. Medicologocal importance in disputed paternity. ## Blood transfusion: - Indications: 1. Decreased blood volume as in hemorrhage. 2. In severe anemia when hemoglobin decreases to 40% (6-8 gm %) or less. 3. In hemorrhagic diseases as hemophilia and thrombocytopenia. 4. In erythroblastosis fetalis. 5. To supply WBCs as in leucopenia. 6. To supply plasma proteins. ## Precautions before blood transfusion: 1. Blood obtained from healthy donors. 2. The transfused blood should be freshly or recently stored (stored at 4 °C for a period 21 days) because in old blood, hemolysis occur → K+ leaves RBCs to plasma so transfusion of such blood may stop heart in diastole. 3. The transfused blood hemoglobin shouldn't less than 90%. 4. Blood grouping is tested for ABO system and Rh factor. 5. The transfused blood should be free from diseases (malaria, syphilis, viral hepatitis and AIDS). ## Dangers: 1. Danger of incompatibility: - Agglutination of the donor's RBCs and may block capillaries (causing severe pain) or block blood vessels of heart (ischemia) or brain (paralysis). - Hemolysis of the agglutinated RBCs leading to hemolytic jaundice and renal failure due to precipitation of hemoglobin and blocking renal tubules. - In addition, hemolysed RBCs release toxic substance → powerful vasoconstriction of blood vessels of the kidney → renal failure. - Hypotension due to histamine liberation from hemolysed RBCs → vasodilatation. - Hyper-kalemia (↑ K+ Level in plasma) → cardiac arrest. 2. Tetany due to decreased the level of Ca++. 3. Transfusion of excess amount → heart failure. 4. Allergy (fever, itching, shivering ......etc). 5. Transmission of diseases as malaria, syphilis, viral hepatitis and AIDS. ## Method: 1. Sterilize the thumb, prick it with sterile pin. 2. Place separate 3 drops on 3 clean glass slides. 3. Place one drop of anti-A on one blood drop, a drop of anti-B on the second blood drop & a drop of anti-D on the third blood drop. 4. Mix the content of each circle with separate toothpicks, wait for few minutes and observe presence or absence of agglutination (clumping) of blood cells, which should occur within 1 minute after mixing. ## Results and possibilities: 1. If agglutination occur with a agglutinin serum → group A. 2. If agglutination occur with β agglutinin serum → group B. 3. If agglutination occur with a and β agglutinin serum → group AB. 4. If no agglutination occur with a and β agglutinin serum → group O. 5. If agglutination occur with D agglutinin serum → Rh positive. ## How to read your results: | Blood Type | Anti-A | Anti-B | Anti-D | |---|---|---|---| | O-POSITIVE | | | | | O-NEGATIVE | | | | | A-POSITIVE | | | | | A-NEGATIVE | | | | | B-POSITIVE | | | | | B-NEGATIVE | | | | | AB-POSITIVE | | | | | AB-NEGATIVE | | | | This description is based on the image and does not include any image within the document itself.