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ABO Blood Groups
| Question | Answer |
|---|---|
| Reagent plant lectin used to differentiate Bombay phenotype | Ulex europaeus |
| Anti-H lectin; yields a negative result with Bombay cells | Ulex europaeus |
| Primary function of ABO, H, and Se genes | code for specific glycosyltransferase enzymes that attach terminal sugars to precursor molecules |
| precursor oligosaccharide chains found in body fluids and secretions | Type 1 |
| precursor oligosaccharide chains found on RBC cell membranes | Type 2 |
| If an antigen (Ag) is present on a patient's red blood cells, the corresponding antibody (Ab) will not be present in the patient's plasma under normal conditions. | Landsteiner's Rule: Reciprocal Relationship |
| Autosomal codominant inheritance; offspring inherits one blood type allele from biological mother and one from biological father | Mendelian genetics of Blood Group inheritance |
| β1-4 linkage | Type 2 found in body fluids and secretions |
| β1-3 linkage | Type 1 found on RBC membranes |
| Predominant immunoglobulin class of Anti-A,B in group O individuals | IgG |
| IgG class of immunoglobulin | capable of crossing the placenta and causing ABO Hemolytic Disease of Fetus and Newborn (HDFN) |
| Immunodominant sugar for the B-antigen | D-galactose (Gal) |
| D-galactose (Gal), immunodominant sugar for the B-antigen is added by this enzyme | D-galactosyltransferase |
| Immunodominant sugar for the H-antigen | L-fucose (Fuc) |
| L-fucose (Fuc), immunodominant sugar for the H-antigen is added by this enzyme | L-fucosyltransferase |
| N-Acetylgalactosamine (GalNAc), immunodominant sugar for the A-antigen is added by this enzyme | N-acetylgalactosaminyltransferase |
| Immunodominant sugar for the A-antigen | N-Acetylgalactosamine (GalNAc) |
| Reagent plant lectin used to differentiate A1 and A2 red blood cells | Dolichos biflorous |
| Anti-A1 lectin; agglutinates A1 cells but not A2 cells | Dolichos biflorous |
| H gene locus chromosome and its dominant/recessive alleles | Chromosome 19: H allele is dominant (>99.99%), h allele is a rare amorph |
| Proportions of A1 and A2 phenotypes among Group A individuals | A1 phenotype ~80%; A2 phenotype ~20% |
| Bombay phenotype | Genotype h/h; lacks H antigen and ABO-antigen expression |
| Bombay phenotype | has strong naturally occurring anti-H, anti-A and anti-B |
| Three separate genetic loci controlling ABH antigen expression | H, Se (Secretor), and ABO |
| Order of blood groups by relative amount of H antigen (greatest to least) | O > A2 > B > A2B > A1 > A1b |
| Safest RBC selection for transfusion in patients with resolved ABO discrepancies or weak subgroups | Group O red blood cells |
| Primary clinical risk associated with weak B subgroups in the blood bank | misidentifying the blood type in the forward typing (eg. mistaking group B for group O or A) leading to ABO incompatible transfusion |
| Predominant immunoglobulin class of naturally occurring ABO antibodies in Group A or B individuals | IgM class |
| Forward typing in ABO testing | detects RBC antigens using commercial antisera |
| Reverse typing in ABO testing | detects plasma antibodies using known reagent red blood cells |
| cross-reacting Anti-A,B antibody | a single IgG antibody found in Group O individuals that reacts with both A and B antigens, not a mixture of anti-A and anti-B |
| a single IgG antibody found in Group _ individuals that reacts with both A and B antigens, not a mixture of anti-A and anti-B | Group O |
| True or False ABO antigens are detectable in utero. | True |
| True or False ABO reciprocal antibodies are detectable at birth | False |
| Prevalence of Anti-A1 antibody in A2 individuals | ~ 8% of A2 individuals |
| Prevalence of Anti-A1 antibody in A2B individuals | ~ 22% - 35% of A2B individuals |
| O allele produces an enzymatically inactive protein, leaving the H antigen unconverted | Group O RBC expression |
| Serological pattern characteristic of B3 subgroup | Mixed-field agglutination when tested with reagent Anti-B |
| Landsteiner's Rule | If an antigen is present on a person's RBCs, the corresponding antibody will NOT be present in their plasma under normal conditions |
| Autosomal codominant inheritance (A and B are codominant, O is recessive) | Mode of inheritance for ABO blood groups |
| Most frequent blood type(s) | Group O and Group A |
| A silent allele that yields no detectable product or enzyme activity (eg: h allele, O allele) | Amorph |
| Naturally occurring antibodies produced against antigens of the same species without foreign RBC sensitization | Isoagglutinins |
| What is Landsteiner's rule, and why does it make forward and reverse typing an internal check for ABO blood group determination? | Forward typing identifies RBC antigens, reverse typing identifies serum antibodies using reagent RBCs. Because the antibody pattern directly mirrors the antigen pattern, the two tests serve as a reciprocal check on each other. |
| Why do Group O red blood cells express the highest quantity of H antigen? | O alleles that produce an enzymatically inactive protein; the H antigen produced by the H gene remains completely unconverted. |
| Why do Group A1B cells express the least H antigen | Group A1B express active A1 and B transferases that convert almost all available H precursor structures leaving very few unconverted H antigen sites. |
| What genetic deficiency causes the Bombay phenotype (Oh), and why can Bombay individuals only receive blood from other Bombay donors? | Without a functional H gene, individuals cannot produce the H antigen required as a foundation for A and B antigens. They naturally form potent Anti-H, Anti-A, and Anti-B antibodies. |
| Why are Group O mothers with IgG Anti-A,B antibodies at higher risk for causing ABO Hemolytic Disease of the Fetus and Newborn (HDFN) compared to Group A or B mothers? | Naturally occurring Anti-A and Anti-B antibodies in Group A and B individuals are predominantly of the IgM class, which cannot cross the placenta. Group O individuals produce a cross-reacting Anti-A,B antibody that is predominantly IgG |
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MOrfCLS
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