ABO Blood Group System

Question 1

What code is associated with the ABO blood group system?

Answer 1

ISBT 001

Question 2

State three reasons as to why the ABO system is important.

Answer 2

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

Question 3

True or false: the ABO system is autosomal co-dominant.

Answer 3

True

Question 4

On which chromosome are the three alleles A, B, and O found?

Answer 4

9

Question 5

True or false: A and B are not co-dominant.

Answer 5

False

Question 6

The ___ gene does not produce a detectable product.

Answer 6

O

Question 7

Name the two other genes which feature in the ABO system, and state where they are found.

Answer 7

H and h; Chromosome 19

Question 8

The H gene produces the ___ antigen.

Answer 8

H

Question 9

The h gene is ______ and rare.

Answer 9

Silent

Question 10

A, B, and H genes code for which type of enzyme?

Answer 10

Glycosyltransferases

Question 11

What is the function of glycosyltransferases?

Answer 11

Transfer sugars onto carbohydrate precursor substances (PS)

Question 12

The __ gene codes for L-fucosyltransferase.

Answer 12

H

Question 13

The A gene codes for __-______________, which transfers to give the A antigen; not all H antigen is converted to A antigen.

Answer 13

N- acetylgalactosaminyltransferase

Question 14

True or false? The B gene codes for D-galactosaminyltransferase; but in a different process than in that observed for the A gene.

Answer 14

False

Question 15

Write a brief note on the Bombay phenotype.

Answer 15

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

Question 16

Precursor substance (PS) + sugar =

Answer 16

Antigen

Question 17

A, B, and H antigens are found in glycolipids and glycoproteins on ____ cells.

Answer 17

Red cells

Question 18

Glycoproteins are only found in _________.

Answer 18

Secretions

Question 19

There are roughly one _______ A1 antigens on a RBC, with a smaller number of H antigens.

Answer 19

Million

Question 20

There are approximately 700,000 ___ antigens, with fewer H antigens, on a RBC.

Answer 20

B

Question 21

Subgroups of A are ____ (80% of the population with Group A blood), and A2 (20%).

Answer 21

A1

Question 22

Anti-___ is made by some of those with A2 or A2B, while Anti-A is made by all those with Groups O and B.

Answer 22

A1

Question 23

True or false: A1 is a better converter of H antigen than A2.

Answer 23

True

Question 24

Anti-__ reacts with A1 and A2 cells; Anti-A1 reacts with A1 cells only.

Answer 24

A

Question 25

True or false? Subgroups of B are very infrequent.

Answer 25

True

Question 26

State the concentration of H antigen on RBC surface of ABO group.

Answer 26

O > A2 > B > A2B

Question 27

ABO antibodies are generally of which class?

Answer 27

IgM

Question 28

True or false: Anti-A and Anti-B are not considered clinically significant.

Answer 28

False

Question 29

Immune forms of ABO antibodies are usually _____.

Answer 29

IgG

Question 30

Secretion of ABH antigens is determined by two _________, Se (dominant) and se (recessive, or amorphic)

Answer 30

Alleles

Question 31

No agglutination in an inhibition test, a negative result, indicates that soluble ___ antigen is present, and the saliva is from a secretor.

Answer 31

A

Question 32

What is the most common cause of ABO grouping discrepancies, and what are some forms of this error?

Answer 32

Technical; transposition errors, clerical errors, missed haemolysis, etc.

Question 33

Weak/missing serum activity may be attributed to:

Answer 33

Extremes of age, and hypogammaglobulinaemia or agammaglobulinaemia; may be remedied by lowering incubation temperature

Question 34

Weak/missing red cell activity may be attributed to:

Answer 34

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)

Question 35

List some reasons for extra serum activity.

Answer 35

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

Question 36

Delineate some causes for extra red cell activity.

Answer 36

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