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| Blood Types Review Complete Review of the ABO and Rh Blood Systems Blood Types - Q&A Review 1. What are the main human blood group systems? In humans the main blood group systems are the ABO system, the Rh system and the MN system. 2. Why is the determination of the blood types of the donor and of the recipient important in transfusions? Red blood cells have different antigens in the outer surface of their plasma membrane; for example, the antigens A and B of the ABO system are glycoproteins of the membrane. If a donor has red blood cells with antigens not present in the red blood cells of the recipient (lacking of transfusion compatibility) the immune system of the recipient recognizes these molecules as actual antigens (i.e., foreign substances) and triggers a defense response producing specific antibodies against those antigens. The transfused red blood cells then are destroyed by these antibodies and the recipient individual may even die. Image Diversity: blood donation 3. What are the antigens and the respective antibodies of the ABO blood group system? The ABO blood system includes the erythrocytic antigens A and B that can be attacked by the antibodies anti-A and anti-B. The antigens A and B are agglutinogens and the antibodies anti-A and anti-B are agglutinins. Blood Types - Image Diversity: ABO system 4. What are the blood types of the ABO blood system? The blood types of the ABO blood system are the type A, the type B, the type AB and the type O. 5. What are the antigens and antibodies of each blood type of the ABO blood system? Type A: antigen A, antibody anti-B. Type B: antigen B, antibody anti-A. Type AB: antigens A and B, does not produce antibody A neither antibody B. Type O: does not have antigen A neither antigen B, has antibodies anti-A and anti-B. (Obviously antibodies are made by B lymphocytes not by red blood cells.) 6. What is the logic of the transfusional compatibility concerning the ABO blood group system? The transfusional compatibility for the ABO system takes into account the antigens present in the red blood cells of the donor and the antibodies that the recipient can produce. Whenever the recipient is not able to produce antibodies against antigens of the red blood cells of the donor the transfusion is compatible. So regarding ABO compatibility type A can donate to type A and to type AB. Type B can donate to type B and to type AB. Type AB can donate only to type AB. Type O can donate to all ABO types. (Any transfusion must be studied, planned and supervised by doctors.) 7. What are universal donors and universal recipients concerning the ABO blood system? Universals donors of the ABO blood type system are the individuals of the type O. Type O blood does not have antigen A neither antigen B in its red blood cells and can be donated to individuals of any ABO type. Universal recipients of the ABO blood type system are the individuals of the type AB. Type AB blood does not contain antibody anti-A neither antibody anti-B and people of this group can receive blood from any of the ABO types. 8. What is the type of genetic inheritance that determines the ABO blood group system? What are the relations of dominance among the involved alleles? The inheritance of the ABO blood system is a multiple alleles inheritance. There are three involved alleles, IA, IB and i that combine in pairs to form the genotypes. Concerning dominance, the allele i is recessive in relation to the alleles IA and IB. Between IA and IB however lack of dominance is established with the heterozygous (IAIB) manifesting distinct phenotype. 9. What are the genotypes and respective blood types of the ABO system? Since the alleles are IA, IB and i the possible genotypes are IAIA (blood type A), IAIB (blood type AB), IBIB (blood type B) and ii (blood type O). 10. Is it possible to perform investigation of natural paternity, maternity or brotherhood and sisterhood using the ABO blood typing? By using the ABO blood typing it is possible only to exclude paternity, maternity or brotherhood/sisterhood but it is not possible to conclude positively about these relationships. For example, if an individual has type O blood, ii genotype, he or she cannot have biological parents of the type AB (IAIB genotype) since necessarily one of his/her alleles has come from the father and the other from the mother. Another example: a couple of individuals of the type O (ii) in their turn can only generate direct offspring of the type O blood, since they do not have alleles that condition antigen A neither antigen B. 11. Is ABO blood compatibility enough for the safety of blood transfusion? Besides ABO blood compatibility the compatibility concerning the Rh blood system must also be checked. In addition it is of fundamental importance for the safety of blood transfusion performing tests to detect agents of main blood transmitted infectious diseases, like HIV (AIDS), hepatitis B and C, syphilis, Chagas disease, etc. (Any transfusion must be studied, planned and supervised by doctors.) 12. What is the Rh factor? RH factor is a protein of the red blood cell plasma membrane that behaves as antigen in blood transfusions triggering a humoral (antibody-based) immune response. Most people present the protein in their red blood cells and are part of the Rh+ group. People that do not have the protein classify as Rh-. The origin of the name Rh factor is related to the first researches that discovered this blood antigen was in rhesus monkeys (Macaca mulatta). Image Diversity: rhesus monkeys 13. How are the antibodies against the Rh factor formed? Anti-Rh antibodies are made by humoral immune response. When an Rh- individual makes contact with the Rh factor this is recognized as foreign (antigen), the primary immune response begins and small amounts of anti-Rh antibodies and memory B lymphocytes are made. In future contact with the antigen there will already be circulating antibodies and memory immune cells prepared to create an intense and effective attack against the Rh factor. 14. What is blood typing? Blood typing is the determination, by means of tests, of the classification of a blood sample concerning blood group systems (specially the ABO system and the Rh system). Blood Types - Image Diversity: blood typing 15. How is the blood typing concerning the ABO system and the Rh usually done? In the blood typing for the ABO system and the Rh system a blood sample is collected from the person and three small volumes of the sample are separated and dispersed on glass laminae (slides). On the first lamina serum containing anti-A antibody is dripped; on the second lamina serum containing anti-B antibody is dripped; on the third lamina serum with anti-RH antibody is dripped. If no agglutination reaction takes place in all of the laminae the blood is of type O- (universal donor); if agglutination occurs only in the first lamina the blood is type A-; and so on. There are other methods of blood typing. Blood typing must be performed by qualified technicians. 16. What are the inheritance and dominance patterns of the Rh blood system? The inheritance pattern of the Rh blood system is autosomal dominant, i.e., the heterozygous manifests as Rh+. The dominance is complete (R is dominant over r). The possible genotypes are RR, Rr (both Rh+) and rr (Rh-). Curiosity: the Rh factor is codified by a gene containing 2790 DNA nucleotides situated in the human chromosome 1. 17. What is the logic of the transfusional compatibility concerning the Rh blood group system? An Rh+ donor can only donate blood to an Rh+ recipient. A person that lacks the Rh factor (Rh-) can donate to individuals of the Rh+ and Rh- groups. 18. What is the Rh typing of the mother and of the fetus in the hemolytic disease of the newborn? In the hemolytic disease of the newborn the mother is Rh- and the fetus Rh+. In this disease antibodies produced by the mother attack the fetal red blood cells. The hemolytic disease of the new born is also known as erythroblastosis fetalis. 19. How does the immune process that causes the hemolytic disease of the newborn take place? In the hemolytic disease of the newborn the mother has Rh- blood. This mother when generating her first Rh+ child makes contact, possibly during delivery, with Rh+ red blood cells of the child and her immune system triggers the primary immune response against the Rh factor. In the next gestation in which the fetus is Rh+ the mother will already have much more anti-Rh antibodies in her circulation; these antibodies cross the placental barrier and gain the fetal circulation causing fetal hemolysis (destruction of the red blood cells of the fetus). Image Diversity: hemolysis 20. How can the hemolytic disease of the newborn be prevented? Erythroblastosis fetalis can be prevented if in the first delivery of a Rh+ child from a Rh- mother serum containing anti-Rh antibodies is given to the mother in the first 72 hours (after the delivery). Therefore the administered anti-Rh antibodies destroy the fetal red blood cells that entered the mother’s circulation before the triggering of her primary immune response. 21. What is the MN blood system? What is the pattern of genetic inheritance of the MN blood system? The MN blood system is a third (in addition to the ABO and the Rh) system of blood antigens also related to proteins of the red blood cell plasma membrane. The inheritance pattern of the MN blood system is autosomal with codominance, a type of lack of dominance in which the heterozygous manifests a phenotype totally distinct from the homozygous. The possible phenotypical forms are three blood types: type M blood, type N blood and type MN blood. |