bb review

What does Landsteiner's Law state?

If an ABO antigen is present on RBCs, the corresponding antibody is absent from the serum, and vice versa.

On which chromosome is the gene for the ABO blood group system located?

Chromosome 9.

The A and B alleles are inherited in what manner?

Codominant.

The O allele is considered what type of gene?

Recessive and amorphic.

What is the most frequent ABO blood type in Caucasians?

Group O (45%).

What is the second most frequent ABO blood type in Caucasians?

Group A (40%).

What is the most frequent ABO blood type in African Americans?

Group O (49%).

What is the second most frequent ABO blood type in African Americans?

Group A (27%).

What is the phenotype of an individual with genotype AA or AO?

Type A.

What is the phenotype of an individual with genotype BB or BO?

Type B.

What is the phenotype of an individual with genotype AB?

Type AB.

What is the phenotype of an individual with genotype OO?

Type O.

What precursor substance must be formed before A or B antigens can be expressed on the red cell?

H substance.

The H gene (FUT1) codes for which enzyme?

α-2-L-fucosyltransferase.

What immunodominant sugar defines H specificity?

L-fucose.

The A allele codes for an enzyme that adds which sugar to the H substance?

N-acetylgalactosamine (GalNAc).

The B allele codes for an enzyme that adds which sugar to the H substance?

D-galactose.

Which ABO group has the highest concentration of H antigen on their red cells?

Group O.

Which ABO group has the lowest concentration of H antigen on their red cells?

Group A₁B.

What is the rare phenotype that results from the inheritance of two nonfunctional H genes (hh)?

Bombay phenotype (Oh).

Why do Bombay (Oh) individuals type as Group O in forward typing?

They lack H antigen, which is the necessary precursor for A and B antigens.

What potent antibody is found in the serum of individuals with the Bombay phenotype?

Anti-H.

Why must Bombay (Oh) individuals be transfused only with other Bombay blood?

Their anti-H is clinically significant and will react with H antigen on all other red cells.

What is the difference between Type 1 and Type 2 precursor chains?

The linkage of the terminal galactose to N-acetylglucosamine (Type 1 is β1→3; Type 2 is β1→4).

Which precursor chain type is found on red blood cells?

Type 2.

Which gene governs the secretion of soluble ABH substances into body fluids?

The Secretor (Se) gene.

An individual with genotype SeSe or Sese is known as a(n) what?

Secretor.

An individual with genotype sese is known as a(n) what?

Non-secretor.

How are A₁ and A₂ subgroups serologically distinguished?

Using anti-A₁ lectin (Dolichos biflorus).

Which subgroup of A reacts with anti-A₁ lectin?

A₁ cells.

Which subgroup of A does NOT react with anti-A₁ lectin?

A₂ cells.

What percentage of Group A individuals are A₁?

~80%.

What percentage of Group A individuals are A₂?

~20%.

Which weaker subgroup of A is known for causing mixed-field agglutination with anti-A?

A₃.

What is the Acquired B phenomenon?

A Group A individual's A antigen is modified by bacterial enzymes to resemble the B antigen.

Acquired B antigen is often associated with diseases of what organ?

The colon or rectum.

What is the typical immunoglobulin class of anti-A and anti-B in Group A and B individuals?

Predominantly IgM.

What is the typical immunoglobulin class of anti-A,B in Group O individuals?

Predominantly IgG.

Are ABO antibodies clinically significant?

Yes, they are the most significant for transfusion practice.

ABO antibodies are efficient binders of what, leading to intravascular hemolysis?

Complement.

What is an ABO discrepancy?

When forward grouping and reverse grouping results do not agree.

What is the most common cause of ABO discrepancies?

Technical errors.

What phenomenon is characterized by a "stack of coins" appearance of RBCs and can cause false-positive agglutination?

Rouleaux.

How is rouleaux resolved in serologic testing?

Saline replacement technique.

What is the blood product of choice for a patient with an unknown blood type requiring red cells?

Group O Rh-negative packed cells.

What is the blood product of choice for a patient with an unknown blood type requiring plasma?

Group AB plasma.

What is unique about Lewis system antigens compared to other blood group antigens?

They are not manufactured on RBCs but are adsorbed from the plasma.

The ability to secrete soluble ABH substances is governed by which gene?

Secretor (Se) gene (FUT2).

Which Lewis phenotype is found in ABH nonsecretors who have at least one Le gene?

Le(a+b-).

Which Lewis phenotype is found in ABH secretors who have at least one Le gene?

Le(a-b+).

What is the most common Lewis phenotype in Caucasians (72%)?

Le(a-b+).

What is the most common Lewis phenotype in African Americans (55%)?

Le(a-b+).

Which Lewis phenotype is more common in African Americans (22%) than in Caucasians (6%)?

Le(a-b-).

Which antibodies are typically IgM, naturally occurring, and generally not clinically significant?

Lewis antibodies (anti-Leᵃ, anti-Leᵇ).

Lewis antibodies are most commonly produced by individuals with which phenotype?

Le(a-b-).

Why don't Lewis antibodies typically cause Hemolytic Disease of the Fetus and Newborn (HDFN)?

They are usually IgM and cannot cross the placenta, and Lewis antigens are not well-developed at birth.

What often happens to the expression of Lewis antigens on a woman's RBCs during pregnancy?

They are decreased or disappear, resulting in a temporary Le(a-b-) phenotype.

The Leᵇ antigen acts as a receptor for which bacterium, associated with peptic ulcers?

Helicobacter pylori.

Who discovered the antibody that led to the naming of the Rh system?

Karl Landsteiner and Alexander Wiener.

The term "Rh positive" refers to the presence of which antigen?

D antigen.

Which Rh antigen is the most immunogenic?

D antigen.

What are the five major antigens of the Rh system in Fisher-Race terminology?

D, C, E, c, e.

What is the purpose of the Rh control in D typing?

To detect false-positive reactions due to spontaneous agglutination.

What test is performed to detect weakened expression of the D antigen?

Weak D (Du) test.

A weak D phenotype due to the C antigen being in the trans position to the D antigen is known as what effect?

Position effect or Ceppellini effect.

A weak D phenotype where an individual is missing one or more epitopes of the D antigen is called what?

Partial D (D mosaic).

According to the Fisher-Race theory, how many closely linked gene loci control the Rh antigens?

Three (D/d, C/c, E/e).

According to the Wiener theory, a single gene at one locus produces what complex product?

An agglutinogen.

Which two genes on chromosome 1 are now known to control the Rh system?

RHD and RHCE.

What is the most common Rh-positive genotype in Caucasians?

R¹r (DCe/dce).

What is the most common Rh-positive genotype in African Americans?

R⁰r (Dce/dce).

What is the most common Rh-negative genotype in both Caucasians and African Americans?

rr (dce/dce).

What is the frequency of the D antigen in the general population?

~85%.

What is the frequency of the c antigen in the general population?

~80%.

What is the frequency of the e antigen in the general population?

~98%.

How do you calculate the number of units to screen to find antigen-negative blood?

(Number of units needed) / (% of population negative for the antigen).

What immunoglobulin class are most Rh antibodies?

IgG.

What is the rare phenotype where individuals lack all Rh antigens on their RBCs?

Rhₙᵤₗₗ.

What is the name of the antibody produced by Rhₙᵤₗₗ individuals that reacts with all cells except other Rhₙᵤₗₗ cells?

Anti-Rh29 (anti-total Rh).

What compound antigen is expressed when c and e are on the same haplotype (cis position)?

f (ce) antigen.

When was the Kell system discovered?

In 1946, after the development of the Coombs test.

What are the three nomenclatures for the Kell system?

Kell (alphanumeric), ISBT (numeric), andpara-Kell (phenotypic).

What is the frequency of the K (K1) antigen in Caucasians?

9%.

What is the frequency of the K (K1) antigen in African Americans?

2%.

What is the frequency of the k (K2) antigen?

99.8%.

What is the frequency of the Jsᵃ (K6) antigen in African Americans?

20%.

What is the frequency of the Jsᵃ (K6) antigen in Caucasians?

What is the frequency of the Jsᵇ (K7) antigen?

99.9% in Whites, 99% in Blacks.

The main Kell antigens are encoded by a gene on which chromosome?

Chromosome 7.

The Kx antigen is encoded by a gene on which chromosome?

X chromosome.

What must be used as a positive control when phenotyping for Kell antigens?

A cell that is heterozygous for the antigen.

Why do K₀ (Kell null) individuals lack all Kell system antigens?

They inherit two rare silent K⁰ genes.

What antibody can K₀ (Kell null) individuals produce?

Anti-Ku (anti-K5).

What rare, X-linked phenotype is characterized by weakened Kell antigens, acanthocytosis, and chronic hemolytic anemia?

McLeod phenotype.

McLeod phenotype results from the absence of which antigen?

Kx antigen.

The McLeod phenotype is associated with which X-linked recessive disorder?

Chronic Granulomatous Disease (CGD).

Outside of ABO and Rh, what is the most common clinically significant antibody seen in the blood bank?

Anti-K (Kell).

What is the immunoglobulin class of most Kell antibodies?

IgG.

Are Kell antibodies clinically significant?

Yes, they cause severe HDFN and transfusion reactions.

How do enzymes like ficin and papain affect Kell antigens?

They do not destroy them.