ABO Blood Group System Flashcards
What code is associated with the ABO blood group system?
ISBT 001
State three reasons as to why the ABO system is important.
If an antigen is lacked, the corresponding antibody will always be present, Anti-A and Anti-B are potent haemolysins, and antibodies are usually IgM
True or false: the ABO system is autosomal co-dominant.
True
On which chromosome are the three alleles A, B, and O found?
9
True or false: A and B are not co-dominant.
False
The ___ gene does not produce a detectable product.
O
Name the two other genes which feature in the ABO system, and state where they are found.
H and h; Chromosome 19
The H gene produces the ___ antigen.
H
The h gene is ______ and rare.
Silent
A, B, and H genes code for which type of enzyme?
Glycosyltransferases
What is the function of glycosyltransferases?
Transfer sugars onto carbohydrate precursor substances (PS)
The __ gene codes for L-fucosyltransferase.
H
The A gene codes for __-______________, which transfers to give the A antigen; not all H antigen is converted to A antigen.
N- acetylgalactosaminyltransferase
True or false? The B gene codes for D-galactosaminyltransferase; but in a different process than in that observed for the A gene.
False
Write a brief note on the Bombay phenotype.
Discovered in India, in 1952; individual was initially typed Group O, with Anti-A and Anti-B present, but had an antibody that reacted with Group O blood. The antibody was later discovered to be anti-H; the genotype was h/h, which is extremely rare
Precursor substance (PS) + sugar =
Antigen
A, B, and H antigens are found in glycolipids and glycoproteins on ____ cells.
Red cells
Glycoproteins are only found in _________.
Secretions
There are roughly one _______ A1 antigens on a RBC, with a smaller number of H antigens.
Million
There are approximately 700,000 ___ antigens, with fewer H antigens, on a RBC.
B
Subgroups of A are ____ (80% of the population with Group A blood), and A2 (20%).
A1
Anti-___ is made by some of those with A2 or A2B, while Anti-A is made by all those with Groups O and B.
A1
True or false: A1 is a better converter of H antigen than A2.
True
Anti-__ reacts with A1 and A2 cells; Anti-A1 reacts with A1 cells only.
A
True or false? Subgroups of B are very infrequent.
True
State the concentration of H antigen on RBC surface of ABO group.
O > A2 > B > A2B
ABO antibodies are generally of which class?
IgM
True or false: Anti-A and Anti-B are not considered clinically significant.
False
Immune forms of ABO antibodies are usually _____.
IgG
Secretion of ABH antigens is determined by two _________, Se (dominant) and se (recessive, or amorphic)
Alleles
No agglutination in an inhibition test, a negative result, indicates that soluble ___ antigen is present, and the saliva is from a secretor.
A
What is the most common cause of ABO grouping discrepancies, and what are some forms of this error?
Technical; transposition errors, clerical errors, missed haemolysis, etc.
Weak/missing serum activity may be attributed to:
Extremes of age, and hypogammaglobulinaemia or agammaglobulinaemia; may be remedied by lowering incubation temperature
Weak/missing red cell activity may be attributed to:
Uncommonly, may be caused by subgroups of A, such as Am, which does not react with Anti-A; may also be due to weak antigenic strength, as seen in forms of leukaemia (Group A is most widely affected)
List some reasons for extra serum activity.
Auto-anti-I is a harmless antibody produced by most people, but it can react at room temperature, or lower (ideally at 4°C), in some people; Anti-A1 can be made by individuals with Group A2 or Group A2B blood; alloantibodies are foreign antibodies; unexpected cold-reactive IgM antibodies, such as Anti-M, Anti-N, etc., may cause A1 or B cells to experience agglutination, and Rouleaux is false agglutination caused by an increase in serum globulins, provided both of the reverse grouping cells are positive
Delineate some causes for extra red cell activity.
Autoagglutinins (excess protein-coating cells) can cause spontaneous clumping; Rouleaux can occur; Acquired B Phenomenon (in-vivo or in-vitro) can occur, leading to bacterial infection due to alteration of the Group A antigen (thus affecting Group A only); some bacteria have determinants which are similar to B antigen; polyagglutination due to T-activation, which is the awakening of the T antigen by bacterial or viral infection, and Wharton’s jelly is a substance present in the umbilical cord; improperly-drawn cord samples will contain Wharton’s jelly; it can mimic an extra antigen
