Chapter 6: The ABO Blood Group System

Approximately how many antigen sites exist on a type-A1 individual's RBC?

1 million

What percentage of the type A population is A2?

20%

Approximately how many antigen sites can be found on A2 cells?

260,000

All of the following is consistent with A3 individuals except?

4,000 antigenic sites on red blood cells

What percentage of the white population has type-O blood?

45%

What percentage of A2 individuals produce anti-A1?

5%

What percentage of individuals inherit the secretor gene?

80%

What percentage of the type-A population are A1?

80%

All of the following is true regarding formation of the ABH antigens except?

A type 1 structure referes to a beta 1-2 linkage

What ABO group contains the least amount of H substance?

A1B

What would a possible genotype of an A2B individual?

A2B

Mixed-field agglutination encountered in ABO forward grouping may be caused by:

A3

Weak agglutination with anti-A typing sera is to be expected with which of the following blood groups?

A3

Reverse grouping showed negative reactions with A1 and B cells. Forward grouping showed positive reactions with A, B, and AB antisera. What blood type is consistent with these results?

AB

Which ABO group's reaction will be the weakest with anti-H lectin?

AB

What other consideration should be made before beginning a subgroup investigation?

ABH alteration caused by malignancy

Which of the following is not characteristic of antibodies within the ABO system?

ABO antibodies do not activate complement

What substances are found in a group A secretor?

AH

Serum from a group B individual contains anti-A. When A2 cells are added to serum and centrifuged, the cells with attached anti-A are removed from serum. What is the name of this technique?

Absorption

A patient who was recently diagnosed with an obstructed bowel became septic from Proteus vulgaris. Prior to surgery, a routine type and screen was performed. Thought this person types as an A two years ago, his forward type is consistent with an AB individual, albeit weaker in strength with anti-B. What is the reason for this discrepancy?

Acquired B

An AB males mates with an AB female. What could be the genotype of the offspring?

All of the above AA, AB, BB

Which of the following criteria is used to classify the B subgroups?

All of the above Agglutination patterns with anti-B, anti-AB, and anti-H Presence of ABH isoagglutinins in serum Absorption studies with anti-B

What testing is available that will differentiate between a true B and an acquire B?

All of the above Anti-B lectin Acidification of anti-B reagent Secretor studies

Cord blood was sent to the laboratory for blood type determination on twins A and B. Baby A demonstrated mixed-field reactions with anti-A and anti-AB and no reactivity with anti-B. Reverse grouping was not performed. Baby B showed a 1+ reaction with anti-A and anti-AB. What could be the reason for the variable reactions?

All of the above Chimerism A dimorphic cell population Dispermy

Where are ABH substances detected in secretors?

All of the above Tears Saliva Milk

If a group O mother gives birth to a group A baby, which of the following antibodies is usually responsible for crossing the placenta and causing hemolytic disease of the newborn (HDN)?

Anti-AB

Why is reverse group not performed on cord blood specimens"

Antibodies are genernally not present at birth

Secretor studies were performed on a person who expressed weak reactions in forward grouping. Only B and H substance were present in the saliva. What is this person's ABO group?

B

What is the source of anti-B lectin?

Bandeiraea simplicifolia

Individuals with group B blood are more common among which populations?

Black/Asian

What does the bb genotype refer to?

Bombay

A patient was previously typed as a blood group O. Forward grouping was negative with anti-A and anti-B. Reverse group showed reactivity with A1 cells and B cells. The technologist reported this patient's type as A. What technical error occurred?

Clerical error

What immunodominant sugar is responsible of B specificity?

D-galactose

Forward grouping is defined as

Detecting antigen(s) on an individual's red blood cells via reagent antisera

What is the most important use for anti-B lectin?

Differentiating a true B from an acquired-like B

What is the source of anti-A1 lectin?

Dolichos biflorus

What is the cause of polyagglutination in most cases?

Exposure of T antigen caused by bacterial contamination

All of the following are technical errors that could result in ABO discrepancies except:

Failure to warm reagents

What is the biochemical structure of secreted A, B, and H substances?

Glycoprotein

Which substance must be formed first before A or B specificity is determined?

H

Anti-A from a group B individual is primarily what class of immunoglobulin?

IgM

An elderly patient is document as being type O. The forward grouping is negative with anti-A and anti-B. The reverse grouping shows no reactivity with A1 cells and B cells. What can be done to correct the discrepancy?

Incubate the patient's serum and reagent cells for 15 minutes at room temperature

What immunodominant sugar is responsible for H specificity?

L-fucose

Persons who inherit the h allele do not produce ________ transferase necessary for formation of the H structure.

L-fucosyl

Which of the following indicates secretor gene control overproduction of H substance?

L-fucosyltransferase is found in the saliva of secretors

All of the following are tests performed in the blood bank to classify subgroups of A except:

LISS enhancement

The ABO group antibodies are primarily

Naturally occuring

If a type-A person contains anti-M in their serum, what might their reverse grouping type as?

O

The forward group of a patient showed no agglutination of patient cells with anti-A, anti-B, or anti-AB reagent antisera. The reverse grouping showed agglutination with A1 and B cells. What is this person's ABO group?

O

What is the only possible phenotype of an offspring produced from two group O parents?

O

Which blood group contains the highest concentration of H antigen?

O

What is used to stimulate saliva secretion in secretor studies?

Paraffin wax

How is polyagglutination resolved?

Patient cells are tested with a lectin panel

A type-A person demonstrates a 3+ reactivity with A1 cells (reverse grouping). The forward grouping with anti-A is 4+. Therefore, the possibility of a subgroup is excluded. B cells demonstrate a 4+ reaction. The antibody screen is weakly positive at 37C, but shows no reactivity at the AHG phase. An antibody panel is performed and anti-M is identified. The patient phenotypes negative for M antigen. How is the ABO discrepancy resolved?

Perform reverse grouping with A1 cells negative for M antigen

How are ABH antigens formed?

Production of specific glycosyltransferases add sugars to precusor substances

A group O person with warm autoimmune hemolytic anemia may demonstrate weak reactions in the forward grouping due to:

Red blood cells being coated with antibody

Two drops of serum are added to one drop of A1 cells, and two drop s are added to one drop of B cells; the two tubes are centrifuged. The tubes show reactivity when read macroscopically. This is an example of:

Reverse grouping

Where will the ABO discrepancy occur in cis-AB individuals?

Reverse grouping with B cells

Reverse grouping was performed on an AB person. The technologist observed a very weak agglutination macroscopically. The cells appeared as "stacked coins" under a microscope. What reagent should be added to the tube before recentrifugation in an attempt to resolve the discrepancy?

Saline

When performing secretor studies, what is omitted in the control tube but present in the patient tube?

Saliva

What is a lectin?

Seed extracts that agglutinate human cells with moderate specificity

All of the following statements are true concerning ABH soluble substances except:

The precursor chain is type 2 (beta 1-4 linkage)

Why can anti-H sometimes be found in an A1B individual?

The specific immunodominant sugar blocks the presence of H antigen

What is the source of anti-H lectin?

Ulex europaeus

Antibody titers specific to antigens from the ABO system are typically highest:

When the patient is around 10 years old

All of the following may depress antigen expression except:

coronary heary disease

All of the following may result in weak or missing antigens except:

hypogammaglobulinemia

All of the following may result in rouleaux formation except:

leukemia

A1 lectin agglutinates:

only A1 cells

The state in which an individual's red blood cells are agglutinated by all sera regardless of blood type is called:

polyagglutination