ABO Blood Group System Overview
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Questions and Answers

All humans possess isoantigens on their red blood cells that are unique to the species.

True (A)

The only blood type that lacks both A and B antigens is known as group AB.

False (B)

The antibodies present in a person's serum are determined by the antigens on their red blood cells.

True (A)

Karl Landsteiner discovered that cross-testing blood samples can identify compatible blood types.

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

Bernstein proposed that there are four allelic genes determining the ABO blood groups.

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

Antigen A is found on individuals who belong to blood group B.

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

Individuals with group A blood will produce antibodies against antigen B.

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

The presence of different red cell antigens is irrelevant to blood transfusion compatibility.

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

The O gene is considered amorphic because it produces detectable antigens.

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

The inheritance of the A and B genes is influenced by the H gene.

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

The A gene produces N-acetyl galactosaminyl transferase.

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

If a person does not inherit at least one H gene, they will still produce the H substance.

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

The B gene produces an enzyme that converts the H substance directly into O antigens.

<p>False (B)</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

The A gene codes for the addition of N-acetylgalactosamine to the H antigen.

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

Individuals with blood type O possess the least amount of H antigen.

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

Group A individuals have more H antigen sites than Group B individuals.

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

Secretors and non-secretors refer to the presence of water-soluble A, B, and H antigen substances in body fluids.

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

About 80% of Caucasians possess the Se gene, which is important for the secretion of blood group antigens.

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

The formation of the B antigen involves the addition of D-galactose to the H antigen.

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

There are equal proportions of Group A1 and Group A2 individuals in the population.

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

The serologic distinction between A1 and A2 is based on the reactions of erythrocytes to various antisera.

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

Type B blood has more common subgroups than type A blood.

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

Acquired A antigen can occur in individuals with type O blood during severe infections.

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

The group A2 contains anti-A1 in up to 2% of its serum.

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

A2B blood typically contains no antibodies in the serum.

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

A superactive B transferase can lead to a deficit of A antigen sites on erythrocytes in some AB individuals.

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

Mixed field agglutination is a reaction visible microscopically when anti-A reagents interact with type AB blood.

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

High levels of soluble ABH substances can suppress the expression of A, B, and H antigens on erythrocytes.

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

Acquired B-like antigen was first recognized in 1959 with conditions such as intestinal obstruction.

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

The deacetylation of the A1 antigen by bacterial enzymes does not cause any change in the antigen.

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

High levels of soluble ABH substances can occur in conditions like ovarian cysts and intestinal obstruction.

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

Weakening of the A antigen is typically not noted in patients with leukemia and lymphoma.

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

Immune antibodies of the P, Lewis, and MN systems are commonly detected and are of significant clinical importance.

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

The M antigen is carried on glycophorin A and is detected on chromosome 4q28-q31.

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

Among white people, the incidence of the M+N- phenotype is 50%.

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

MN antibodies react at temperatures only up to 37°C.

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

The K antigen is found in 9% of the English population.

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

The Jsa antigen is present at a frequency of 99.9% in the Caucasian population.

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

The genes associated with the Kell antigen system include K, k, Kpa, Kpb, Jsa, and Jsb.

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

Individuals with Kell antigens are known to have no association with transfusion reactions.

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

MN antigen is generally considered clinically significant at a temperature of 37°C.

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

Flashcards

ABO Blood Group System

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

Isoantigens

Antigens unique to a particular species, including humans.

Alloantigens

Antigens common to some but not all members of a species, capable of triggering antibody production in those lacking them.

Blood Group A

Red blood cells possessing only the A antigen.

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Blood Group B

Red blood cells possessing only the B antigen.

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Blood Group AB

Red blood cells possessing both A and B antigens.

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Blood Group O

Red blood cells lacking both A and B antigens.

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Agglutination

The clumping of red blood cells when incompatible blood types are mixed.

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O Gene Inheritance

The O gene is an amorphic gene, meaning it doesn't produce a detectable antigen, or enzyme, and no H substance.

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A and B blood type genes

The A and B genes produce enzymes (transferases) that alter the H substance to form the A or B antigens. The presence of these genes determines whether A, B, or neither antigen is expressed in body fluids and red blood cells

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H gene function

The H gene produces the enzyme L-fucosyl transferase, which adds L-fucose to the precursor substance, creating the H substance.

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Relationship between genes and blood type expression

Blood types A, B, and O are produced based on an inheritance of genes that determine whether the precursor substance is converted to A, B, or neither antigen using enzymes.

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Mendelian inheritance of blood type

Blood type inheritance follows a dominant and co-dominant pattern. A and B are dominant to O, and A and B are co-dominant.

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H Antigen

The foundation for A and B antigens; a carbohydrate structure on red blood cells.

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A and B Antigens

Specific carbohydrate structures on red blood cells, determined by the A and B genes, which code for enzymes that add sugar to the H antigen.

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Blood Type O

O blood types have more H antigen than others, as the O gene is essentially a no-op gene when constructing the H antigen. It doesn't alter the structure of the H antigen.

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Secretor Gene (Se)

A gene influencing the presence of water-soluble A, B, and H antigens in body fluids.

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A1 and A2 Subgroups

Two subtypes of the A blood type determined by genetic differences. A1 is more prevalent.

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N-acetylgalactosamine

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

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D-galactose

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

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Blood Type Groups

Blood types (O, A1, A2, B, A1B, A2B) are determined by the specific sugars attached to the H antigen.

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Kell Blood Group System

A blood group system characterized by the Kell antigen, which is clinically significant due to its potential for causing transfusion reactions and hemolytic disease of the newborn (HDN).

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Kell Antigen

A protein found on the surface of red blood cells, responsible for the Kell blood group system.

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Kell Blood Group System Incidence

The frequency of Kell blood types varies in different populations. For example, the K antigen is more common in English populations than in Black populations.

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Kell Antigen Function

The Kell antigen, a zinc metalloprotein, has endopeptidase activity, playing a role in cell processes related to its function.

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Kell Antigen Chromosomal Location

The Kell antigen gene is located on chromosome 7q33, a specific region of chromosome 7.

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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 antisera, particularly anti-A serum from a Group B individual.

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Anti-A1 Antibody

Some A2 or A2B individuals have antibodies in their serum that specifically target the A1 antigen.

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A2 Importance in Transfusion

The A2 blood type is less reactive and doesn't usually require special attention in transfusions, except when working with A2 or A2B individuals who possess anti-A1 antibodies.

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B Subgroups

There are several subgroups or variants of the B blood type, though they're less common than A subgroups.

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B Subgroup Classification

The classification of B subgroups has involved factors like race and Sanger's research.

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Modifying Genes

In some cases, the presence of specific genes can modify the expression of ABH antigens on red blood cells, affecting the blood type.

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Acquired A Antigen

Under specific conditions, such as severe infections with Proteus mirabilis, individuals of blood types O or B can acquire an A antigen.

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Acquired A Antigen Reactions

The acquired A antigen can lead to mixed field agglutination when reacting with anti-A serum, meaning some cells clump together while others don't.

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Acquired B-like Antigen

A temporary expression of the B antigen in individuals with blood type A, usually caused by bacterial infection.

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A1 Phenotype

Individuals with the A1 blood type are more susceptible to acquiring the B-like antigen due to the specific structure of their A antigen.

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Deacetylation

The removal of an acetyl group from a molecule, specifically the A1 antigen in this case, leading to a change in its structure and potential expression of B antigen.

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Soluble ABH Substances

Free-floating molecules in the blood that contain the A, B, or H antigens. High levels can interfere with blood typing tests.

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Neutralization

The inactivation of antibodies (anti-A or Anti-B) by soluble ABH substances, preventing them from reacting with blood cells in a typing test.

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Depression of A, B, and H Substances

A decrease in the levels of A, B, or H antigens on red blood cells, potentially caused by medical conditions like leukemia or lymphoma.

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MNSs Blood Group System

A blood group system less clinically significant than ABO, determined by proteins called glycophorins A and B.

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MN and Ss Antigens

Proteins expressed on red blood cells belonging to the MNSs blood group system.

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Study Notes

The ABO Blood Group System

  • The ABO blood group system is a classification of human blood types based on the presence or absence of specific antigens (A and B) on the surface of red blood cells (RBCs) and corresponding antibodies in the blood plasma.
  • Different blood types have specific antigens present on their RBCs. These antigens are unique for each species.
  • Isoantigens are inherited antigens found on RBCs that are unique to a particular species.
  • Alloantigens are antigens found in some members of a species but not all. They can induce alloantibodies in individuals who lack them
  • Blood group serology involves detecting these antigens and antibodies, essential for blood transfusions.
  • Karl Landsteiner's discovery in the early 20th century revolutionized blood transfusions, demonstrating that incompatible blood mixing could lead to severe reactions. Cross-testing blood samples showed that some mixed successfully while others reacted strongly, highlighting the importance of compatibility testing.
  • Agglutination (clumping) of red blood cells occurs when an antigen on the RBC surface interacts with an opposing antibody in the serum.
  • The ABO system comprises four blood types: A, B, AB, and O. Individuals with type A blood have only A antigens on their RBCs, type B have only B antigens, type AB have both A and B antigens, and type O have neither A nor B antigens.

Blood Group Antigens

  • The A and B antigens develop on the surface of red blood cells based on the H antigen, existing as a precursor substance.
  • The H antigen is formed when L-fucose is added to the precursor substance.
  • The A gene produces N-acetylgalactosaminyltransferase to add N-acetylgalactosamine sugar to the H antigen.
  • The B gene produces D-galactosyltransferase, adding D-galactose sugar to the H antigen
  • The O gene doesn't produce a transferase enzyme.

Gene Sequence

  • In 1924, Bernstein postulated three allelic genes (A, B, and O) controlling the ABO blood group system, inheriting one gene from each parent.
  • The O gene is considered amorphic because no detectable antigen is produced in response to its inheritance.

Blood Group Antigens Expression

  • The expression of A and B genes on RBCs and body fluids is based on inheriting Hh, Sese, and A and B genes, with the latter located on chromosome 9 and the former on chromosome 19.

Secretion of Antigens

  • The presence of the Se gene influences the secretion of A, B, and H antigens in body fluids, essential for testing in various situations.

Type A Subgroups

  • The A antigen group can be divided into subgroups like A1 and A2, with A1 being more prevalent (80%). A2 shows weaker reactions.

Type B Subgroups

  • Type B blood subgroups are less common than A subgroups.

Other Blood Group Systems

  • Other blood groups, such as MNSS, Kell, Lewis, Duffy, Kidd, and others, are present within the human population.
  • These blood systems are less clinically important than ABO or Rh.
  • Antibodies in these systems sometimes appear under different conditions.
  • Several blood-type systems are known but the clinical importance of most groups, while present, is only in rare cases

Rh System (Rhesus Factor)

  • Discovered by Landsteiner, Wiener, and Levine/Stetson.
  • Presence/absence of the RhD antigen is crucial.
  • Absence (Rh−) of the RhD antigen in a mother can lead to hemolytic disease when a fetus (Rh+) inherits a different condition.
  • Rh antibodies produced in the mother during pregnancy can destroy the fetal RBCs leading to complications
  • Various combinations of related blood group antigens exists (CDEcde) on the same chromosome.

Antibody Types

  • Naturally occurring antibodies may be present if the antigen is absent
  • Reactive at 37°C are called warm antibodies like Anti-D
  • Reactive at 4°C are called cold antibodies like Anti-A and Anti-B
  • Immune antibodies are generated in response to antigen exposure.

Useful applications of Blood Groups

  • Used to prevent transfusion reactions
  • Used in forensic science and paternity testing
  • To identify disease states, such as those impacting RBCs
  • Important for organ transplantations

Detection of Blood Groups

  • Antibody screening and cross-matching tests are frequently employed in transfusion medicine to assess blood group compatibility.
  • Agglutination of red blood cells with specific antibodies is a standard method of identification.
  • Coombs tests are crucial for diagnosing conditions like autoimmune hemolytic anemia.

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Related Documents

The ABO Blood Group System PDF

Description

Explore the ABO blood group system, a fundamental classification of human blood types based on the presence of antigens on red blood cells. Understand the roles of isoantigens and alloantigens in blood compatibility and the historical significance of Karl Landsteiner's discoveries in blood transfusion practices.

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