ABO Blood Group System

• Blood typing test determines a person's blood type by the presence or absence of antigens A and B on red blood cells

  
• Results of a blood typing test:

  • Type A blood: clumps with anti-A antibodies
  • Type B blood: clumps with anti-B antibodies
  • Type AB blood: clumps with both anti-A and anti-B antibodies
  • Type O blood: does not clump with either anti-A or anti-B antibodies
• ABO blood group system:

  • Discovered by Dr. Karl Landsteiner via mixing cells and serum, observing agglutination
  • Main blood group in transfusion practice
  • Individuals have antibodies in their serum against antigens absent from their RBCs, which can lead to transfusion reactions if incompatible
• ABO inheritance:

  • Follows simple Mendelian genetics
  • ABO genes are inherited one from each parent
  • A, B, or O gene is located on Chromosome 9
  • Group O gene is an autosomal recessive trait with two nonfunctional O genes
• Formation of ABH antigens:

  • Depends on ABO, Hh, and Se genes
  • Develops in the second month of fetal life and remains throughout life
  • RBC ABO antigens are constructed from Type 2 precursors
• Blood typing test determines a person's blood type by the presence or absence of antigens A and B on red blood cells: type A has A antigens, type B has B antigens, type AB has both, and type O has neither

  
• Blood typing test is done by mixing blood with anti-A and anti-B antibodies: clumping indicates presence of respective antigens
• ABO blood group system:

  • Most common Group O01 results from a single nucleotide deletion near the N-Terminus causing frameshift and a truncated product with no enzyme activity
  • Group O02 has a nucleotide deletion and nine point mutations
• ABH Antigens in ABO system are carbohydrate structures on glycoproteins and glycolipids, found on RBC membrane proteins, platelets, and other tissues like lungs, gut, urinary, and reproductive tracts
• ABO incidence:

  • Group B is common in African Americans and Asians
  • Group A and O are most common, found in Asians
  • Group AB is the rarest
• H antigen is the basic antigenic material of ABO, found in greatest concentrations on RBCs of group O individuals, detected by anti-H antiserum
• Secretor genes control the presence of A and B on secretions, with ABH antigens found in secretions of people with the secretor phenotype (Se)
• Bombay phenotype results from inheritance of hh gene, causing no H substance, no ABH antigens, and is transfused with Bombay phenotype cells
• Para-Bombay phenotypes lack H antigens or have small amounts present, expressing weak forms of A and B antigens detected in elution techniques
• ABO subgroups:

  • A subgroups are more common than B subgroups, with A1 positive being clinically significant
• A2 individuals produce Anti-A1 due to polymorphisms at the ABO locus, with A2 resulting from a single-base substitution at nucleotide 1059
• ABO antibodies:

  • Develop naturally or immune, peak at age 5-10
  • React at room temperature, also present in plants and animals
• The ABO blood group system classifies blood into four types: A, B, AB, and O based on the presence or absence of two antigens, A and B, on the surface of red blood cells

  
• In the ABO blood typing test, if blood has A antigens, it clumps in the presence of anti-A antibodies; if it has B antigens, it clumps in the presence of anti-B antibodies; if it has both A and B antigens, it clumps in the presence of both anti-A and anti-B antibodies; if it has neither A nor B antigens, it doesn't clump in the presence of either anti-A or anti-B antibodies
• Forward grouping involves adding a patient's red blood cells to commercial antisera to detect antigens, while reverse grouping detects ABO antibodies in the patient's serum using known reagent red blood cells (A1 and B cells)
• Technical errors in blood banking include improper identification of blood specimens, clerical errors, cell suspension problems, failure to add reagents, mix-up in samples, missed observation of hemolysis, uncalibrated centrifuge, contaminated reagents, and warming during centrifugation
• The ABO blood group system classifies blood into types: A, B, AB, and O based on the presence or absence of antigens A and B on red blood cells

  
• Blood typing determines a person's blood type by mixing their blood sample with anti-A and anti-B antibodies to observe clumping reactions
• Type A blood has only A antigens, type B has only B antigens, type AB has both A and B antigens, and type O has neither A nor B antigens
• In blood typing, clumping in the presence of anti-A antibodies indicates A antigens, clumping with anti-B antibodies indicates B antigens, clumping with both indicates AB, and no clumping indicates type O
• Factors causing discrepancies in blood typing results include ABO subgroups, disease conditions like low antigen expression in leukemia or lymphoma, and protein abnormalities
• Resolution methods for discrepancies in blood typing include enhancing serum reactions, incubating mixtures at different temperatures, and using saline replacement techniques to remove contaminating substances