ABO Blood Group System Overview
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Questions and Answers

The O gene is considered dominant because it produces detectable antigens in response to inheritance.

False (B)

The A and B genes are co-dominant and are responsible for producing transferases that convert the H substance to A and B antigens.

True (A)

Inheritance of at least one H gene is necessary for the formation of the H substance.

True (A)

The H gene codes for the production of D-galactosyl transferase.

<p>False (B)</p> Signup and view all the answers

The Se gene is responsible for the expression of H only on erythrocytes.

<p>False (B)</p> Signup and view all the answers

The prevalence of the K antigen is 9% in the Black population.

<p>False (B)</p> Signup and view all the answers

MNSs are associated with resistance to Plasmodium falciparum invasion.

<p>True (A)</p> Signup and view all the answers

Kell antigens are zinc metalloglycoproteins that possess neutral endopeptidase activity.

<p>True (A)</p> Signup and view all the answers

The MNS system plays a major role in determining blood transfusion compatibility.

<p>False (B)</p> Signup and view all the answers

Kpb antigen is present in 99.9% of the Caucasian population.

<p>True (A)</p> Signup and view all the answers

Acquired B-like antigen was first recognized in 1959.

<p>True (A)</p> Signup and view all the answers

The acquired B-like antigen is permanently retained by patients after recovery from infection.

<p>False (B)</p> Signup and view all the answers

The acquisition of B antigen usually occurs in persons with the A2 phenotype.

<p>False (B)</p> Signup and view all the answers

High levels of soluble ABH substances can inhibit the anti-A or anti-B reagent.

<p>True (A)</p> Signup and view all the answers

Weakening of the A antigen is only noted in patients with infections.

<p>False (B)</p> Signup and view all the answers

Naturally occurring antibodies of the P, Lewis, and MN system are clinically significant.

<p>False (B)</p> Signup and view all the answers

The MN antigen is encoded by genes located on chromosome 4q28-q31.

<p>True (A)</p> Signup and view all the answers

The MNS blood group system is clinically significant due to its high immunogenicity.

<p>False (B)</p> Signup and view all the answers

Isoantigens are unique to each species, including humans.

<p>True (A)</p> Signup and view all the answers

Alloantigens are present in every individual of a species.

<p>False (B)</p> Signup and view all the answers

Karl Landsteiner discovered that blood samples can react strongly or mix without reaction when cross-tested.

<p>True (A)</p> Signup and view all the answers

Group AB blood cells have neither A nor B antigens on their surface.

<p>False (B)</p> Signup and view all the answers

The antibody that reacts with B cells is called Anti-A.

<p>False (B)</p> Signup and view all the answers

Bernstein proposed that there are three allelic genes: A, B, and O.

<p>True (A)</p> Signup and view all the answers

Individuals inherit two ABO genes, one from each parent.

<p>True (A)</p> Signup and view all the answers

Anti-A antibodies are present in the serum of individuals with Group A blood.

<p>False (B)</p> Signup and view all the answers

The H antigen is important because it is the foundation upon which the A and B antigens are built.

<p>True (A)</p> Signup and view all the answers

The O allele alters the structure of the H antigen.

<p>False (B)</p> Signup and view all the answers

Group A individuals have the greatest amount of H antigen compared to other blood types.

<p>False (B)</p> Signup and view all the answers

A typing serum prepared from anti-A of a group B person adsorbed with A2 cells will agglutinate A2 but not A1 erythrocytes.

<p>False (B)</p> Signup and view all the answers

The presence of the Se gene determines whether an individual is a secretor or non-secretor of ABH antigens.

<p>True (A)</p> Signup and view all the answers

All individuals with blood group A possess the same amount of H antigen.

<p>False (B)</p> Signup and view all the answers

Distinguishing between A1 and A2 blood types is critical for routine blood transfusions.

<p>False (B)</p> Signup and view all the answers

There are three known subgroups of type B blood.

<p>True (A)</p> Signup and view all the answers

D-galactosyltransferase is the enzyme coded by the A gene.

<p>False (B)</p> Signup and view all the answers

A2B individuals' serum may contain anti-A in levels up to 25%.

<p>True (A)</p> Signup and view all the answers

Individuals with Group A blood only have A antigens on their red blood cells.

<p>False (B)</p> Signup and view all the answers

There are equal percentages of A1 and A2 subgroups in blood group A.

<p>False (B)</p> Signup and view all the answers

The presence of a superactive B transferase does not affect the expression of A antigens on erythrocytes.

<p>False (B)</p> Signup and view all the answers

Acquired A antigen can occur in individuals with type O blood as a result of severe infections.

<p>True (A)</p> Signup and view all the answers

Mixing of blood does not affect the expression of ABH antigens on erythrocytes.

<p>False (B)</p> Signup and view all the answers

The Khosian people of South Africa have the highest frequency of the Bantu A subtype.

<p>True (A)</p> Signup and view all the answers

Flashcards

O Gene Inheritance

The O gene does not produce any transferase enzyme, resulting in no detectable substance (H) production.

A and B Gene Inheritance

A and B genes are inherited independently of H, Sese genes, producing either A or B antigens on erythrocytes (red blood cells) or body fluids.

H Gene Function

The H gene codes for L-fucosyl transferase, an enzyme that adds L-fucose to the precursor substance, creating the H substance.

A and B Gene Transferases

The A gene produces N-acetylgalactosaminyl transferase, and the B gene produces D-galactosyl transferase, which convert the H substance into A and B antigens, respectively.

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Inheritance Pattern (A, B, O)

A and B are dominant to, but co-dominant to each other, while O is recessive; following a Mendelian inheritance pattern.

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ABO Blood Group System

A system classifying blood types based on the presence or absence of antigens (A and B) on red blood cells and corresponding antibodies (anti-A and anti-B) in the blood serum.

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Isoantigens

Inherited antigens specific to a species, including humans, found on the surface of red blood cells.

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Alloantigens

Antigens common to some, but not all, members of a species; capable of inducing antibody production in those lacking the antigen.

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Blood Group Antigens (A & B)

Specific proteins/carbohydrates found on the surface of red blood cells, defining blood groups A, B, AB, and O.

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Blood Group A

Red blood cells with only the A antigen.

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Blood Group B

Red blood cells with only the B antigen.

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Blood Group AB

Red blood cells with both A and B antigens.

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Blood Group O

Red blood cells with neither A nor B antigens.

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H antigen

The foundation upon which A and B antigens are built.

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A and B antigens

Created by enzymes adding sugars to the H antigen; specificity determined by terminal sugars.

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N-acetylgalactosamine

Sugar added to the H antigen by the A gene's enzyme.

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D-galactose

Sugar added to the H antigen by the B gene's enzyme.

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O allele

A silent allele, meaning it doesn't affect the H antigen structure, resulting in more of it.

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Secretors

Individuals with soluble ABH antigens in body fluids, determined by the Se gene, about 80% of Caucasians.

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Group A sub-groups (A1/A2)

Differentiated based on genes coding for enzymes adding slightly different things.

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ABO blood types

Blood types determined by the presence of the A, B, or O alleles resulting in different enzymes adding different sugars to the H antigen.

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A1 vs A2 Distinction

The difference between A1 and A2 blood types is determined by how their red blood cells react to specific antibodies (antisera). A1 cells react strongly with anti-A, while A2 cells react weakly.

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Anti-A1 Antibody

Some people with A2 or A2B blood type may have an antibody in their serum called anti-A1, which can react with A1 red blood cells.

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B Subgroups

There are different variations of the B blood type (B subgroups), though they aren't as common as the A subgroups.

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A2 Importance in Transfusion

While A1 and A2 are usually treated the same for blood transfusions, it's important to distinguish them when working with A2 individuals with anti-A1 in their serum.

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Modifying Genes

Sometimes, genes can influence how the A or B antigens are expressed on red blood cells. For example, a 'superactive' B gene can lead to fewer A antigens, despite the presence of the A gene.

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Acquired A Antigen

In rare cases, people with type O or B blood can temporarily develop an A antigen due to infections, like those caused by the bacteria Proteus mirabilis.

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Levine Hypothesis

This hypothesis suggests that sometimes A and B antigens appear on red blood cells even without the usual H substance. It's thought to be caused by a 'suppressor gene' at the Hh locus.

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Alternative Pathway

Some researchers believe that there might be another way to create A antigens (and possibly B antigens) independent of the usual pathway.

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Acquired B-like Antigen

A temporary presence of the B antigen in individuals with the A1 blood group, often occurring due to bacterial infections.

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Cause of Acquired B-like Antigen

The A1 antigen can be altered by bacterial enzymes (deacetylation) during infections, resulting in the appearance of the B antigen.

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Loss of Acquired B-like Antigen

After recovery from the infection, the acquired B-like antigen disappears, and the individual returns to their original blood group.

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High Soluble ABH Substances

Elevated levels of soluble A, B, or H substances in body fluids can occur due to various conditions like cysts, intestinal obstruction, and cancers.

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Neutralization of Reagents

Elevated soluble ABH substances can neutralize anti-A or anti-B reagents, potentially interfering with blood typing tests.

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MNSs System

A blood group system with clinically insignificant antigens, except for the M, N, and S antigens which have some importance.

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MNSs Antigens

The MNSs system includes the M, N, and S antigens, found on proteins called glycophorins.

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Clinical Importance of MNSs System

The MNSs system is generally of low clinical importance, but some antigens can cause mild transfusion reactions.

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Kell System

A blood group system with several antigens, including K, k, Kpa, Kpb, Jsa, and Jsb. The Kell system's primary antigen is Kell (KEL) and is considered clinically significant, often implicated in transfusion reactions and hemolytic disease of the newborn (HDN).

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Kell System's Clinical Significance

The Kell blood group system is clinically significant due to the potential for severe immune responses, including transfusion reactions and hemolytic disease of the newborn (HDN). Individuals with the Kell antigen (KEL) are at risk of developing antibodies against this antigen, which can lead to life-threatening complications.

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Kell System's Function

The Kell antigens are transmembrane proteins that play a role in cell signaling and interactions. However, the exact function of the Kell system is not fully understood.

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Kell System's Composition

Kell antigens are zinc metalloproteins with neutral endopeptidase activity. This means they bind zinc and can break down proteins in the cell membrane.

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Kell System's Location

Kell antigens are located on a specific protein (93 kD transmembrane protein) on the surface of red blood cells (RBCs).

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Study Notes

ABO Blood Group System

  • Blood group antigens are inherited factors found on red blood cells
  • Isoantigens are antigens unique to each species
  • Alloantigens are antigens common to some but not all members of a species
  • Blood group serology identifies these antigens and corresponding antibodies

Discovery of Blood Groups

  • Karl Landsteiner's research in the early 20th century showed that blood samples mix differently when cross tested
  • Agglutination (clumping) was attributed to the presence of specific antigens on red blood cells and matching antibodies in the serum
  • Different red blood cell antigens were identified as A and B
  • Blood types are classified as A, B, AB, and O, based on the presence or absence of antigens A and B on the surface of red blood cells.

ABO Blood Groups: Antigens and Antibodies

  • Individuals with type A blood cells have only antigen A

  • Individuals with type B have only antigen B

  • Individuals with type AB blood have both antigens A and B

  • Individuals with type O blood have neither antigen A nor B

  • Individuals with type A blood have anti-B antibodies in their plasma

  • Individuals with type B blood have anti-A antibodies in their plasma

  • Individuals with type AB blood have neither anti-A nor anti-B antibodies in their plasma

  • Individuals with type O blood have both anti-A and anti-B antibodies in their plasma

ABO Blood Group Genetics

  • Blood type is determined by three alleles (variants of a gene): A, B, and O
  • Individuals inherit two alleles, one from each parent
  • The O allele is considered recessive to A and B alleles
  • A and B alleles are codominant (both expressed if present)

The H Gene

  • The H gene codes for L-fucosyltransferase, an enzyme that adds L-fucose to the precursor substance
  • The H substance acts as a foundation (precursor) for A and B antigens
  • People with certain blood groups (e.g. type O) have naturally occurring more H antigens compared to others

A and B Antigens

  • The A gene codes for N-acetylgalactosaminyltransferase
  • The B gene codes for galactosyltransferase
  • These transferases add specific sugars to the H antigen (creating A and B antigens)

Secretor Status

  • The Se gene is responsible for the expression of A, B, and H antigens in body fluids like saliva, plasma, etc.
  • 80% of Caucasians are secretors

Blood Group Subgroups

  • A blood types can be further subdivided into A1 and A2
  • 80% of individuals with type A are A1, 20% are A2

Other Blood Group Systems and Antigens

  • Other blood group systems exist (besides ABO), each with its own antigens and subtypes
  • Some, including MN, P, Kell, Lewis, Duffy, Kidd, and Rh, are important for clinical purposes for transfusion and transplantation

Detection of Blood Groups

  • Detection methods often involve antibodies and agglutination which is used to detect blood typing
  • Typically performed via antibody screening and cross matching process

Function of Antigens and Antibodies

  • The presence and type of antigens determines the blood type
  • The presence and type of antibodies in plasma ensures blood compatibility between donors and recipients

Rh System Features

  • Discovered by Landsteiner and Wiener, and later researched by Levine and Stetson
  • The Rh system is complex with several different antigens and variants
  • The RhD antigen is critical to the Rh system which has several related proteins coded by multiple genes
  • RhD inheritance largely determines Rh status (D+) or (D-) as positive or negative

Rh System Genetics

  • The Rh factors are carried on a single chromosome (involving several different alleles)

Inheritance of Rh Genes and Factors

  • The Rh system is inherited through a Mendelian pattern via several possible combinations
  • Blood typing via antibodies is dependent upon antigen present

Direct and Indirect Coombs Tests

  • Techniques for detecting antibodies attached to red blood cells
  • Distinguished on their functions

Clinical Significance

  • Blood typing is crucial for preventing transfusion reactions and hemolytic disease of the newborn
  • Used in forensic science and paternity testing to identify individuals.

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Related Documents

The ABO Blood Group System PDF

Description

Explore the ABO blood group system, including the inheritance of blood group antigens and the discovery made by Karl Landsteiner. Understand the significance of isoantigens and alloantigens, and how blood types A, B, AB, and O are classified. This quiz will enhance your knowledge of blood group serology and its applications.

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