Ii Blood Group

Question 1

The branching process is controlled by______ enzymes, which add sugars to the straight chains of i, converting them into branched I structures

Answer 1

glycosyltransferase enzymes

Question 2

• Newborns predominantly express the____ antigen (their RBCs are rich in linear carbohydrate chains).

• Over the first 18 months of life, the____ antigen decreases as enzymatic branching converts it into____ antigen.

• By adulthood, RBCs contain predominantly____ antigen with only trace amounts of___ remaining

Answer 2

i antigen

i; I

I; i

Question 3

Some individuals do not undergo this normal transition and retain the i antigen into adulthood. These individuals have the_____phenotype, which is genetically distinct and results from mutations affecting the enzyme responsible for branching.

Answer 3

i adult

Question 4

_____ is a common naturally occurring antibody.

• Cold-reacting IgM antibody, often seen in healthy individuals.

• Can cause cold agglutinin disease (CAD), a type of autoimmune hemolytic anemia where RBCs clump at cold temperatures.

Answer 4

Anti-I

Question 5

____is much rarer but can be associated with:

• Some cases of infectious mononucleosis (caused by Epstein-Barr virus)
• Certain hematologic disorders

Answer 5

Anti-i

Question 6

Proteolytic enzymes (2) enhance the reactivity of both I and i antigens with their respective antibodies.

Answer 6

ficin and papain

Question 7

(2) do not destroy I and i antigens, meaning they are resistant to these chemical treatments.

Answer 7

Dithiothreitol (DTT) and glycine-acid EDTA

Question 8

______ is commonly associated with cold agglutinin syndrome (CAS), where the antibody binds to I-positive RBCs at low temperatures.

• This can lead to hemolysis (destruction of RBCs) when the immune system mistakenly attacks them.

Answer 8

Anti-I

Question 9

•_____ is sometimes detected in patients with infectious mononucleosis, where the Epstein-Barr virus (EBV) triggers an immune response.

• This antibody is usually transient and not clinically significant.

Answer 9

Anti-i

Question 10

• I antigen is formed by the action of the IGnT gene, which is located on chromosome____

Answer 10

6

Question 11

formation is not entirely understood, but it serves as the precursor for I antigen.

Answer 11

i antigen

Question 12

As the person matures, small i antigen is enzymatically converted into branched I antigen with the help of the______.

Answer 12

IGnT gene

Question 13

Molecular Structure

• Both I and i antigens are formed on precursor______ chains of RBCs.

Answer 13

A, B, and H

Question 14

The H antigen substrate and I antigen share the same precursor:

• ______+______

• However, the I antigen lacks additional sugars, such as fucose and/or galactose, which are present in H antigen.

Answer 14

Lactosylceramide + Paragloboside

Question 15

_____+_______+______→ i Antigen (Linear, small structure)

Answer 15

Lactosylceramide (Glc-Gal) +
N-acetylglucosamine +
Galactose

Question 16

→ I Antigen (Branched, larger structure)

Answer 16

i Antigen +
N-acetylglucosamine +
Galactose

Question 17

facilitates the conversion of small i antigen into big I antigen.

Answer 17

IGnT gene

Question 18

Ii Antigens and Their Reactions with Antibodies

• Enzymatic Effects: (2)

• Resistant to:

Answer 18

• Ficin → Produces 2 end products
• Papain → Produces 3 end products

• Dithiothreitol (DTT)
• Glycine-acid EDTA

Question 19

In adults (I antigen present): _____strongly reacts because I antigen is dominant.

Answer 19

Anti-I

Question 20

In newborns (i antigen dominant): ____reacts strongly since I antigen has not yet developed.

Answer 20

Anti-i

Question 21

In the rare adult i phenotype: Since conversion is incomplete, i antigen remains, leading to a strong reaction with____ and weak reaction with____.

Answer 21

anti-i

anti-I

Question 22

• Clinically insignificant → Does not cause hemolysis or any blood-related disorder.

Answer 22

Benign Autoanti-I

Question 23

• It is naturally occurring and non-pathologic (does not cause disease).
• Common in virtually all individuals (trace amounts present in normal sera).
• Reacts at 4°C (cold IgM autoantibody).

Answer 23

Benign Autoanti-I

Question 24

• Causes Cold Agglutinin Disease (CAD), a type of autoimmune hemolytic anemia

Answer 24

Pathologic Autoanti-l

Question 25

• IgM in nature but pathogenic. • Produced after Mycoplasma pneumoniae infection. • Reacts at room temperature and at 4°C, meaning it can agglutinate RBCs even at normal body temperatures.

Answer 25

Pathologic Autoanti-l

Question 26

• Very rare because most adults have the I antigen. • Present in individuals with the adult i phenotype (who fail to convert i antigen to I). • Can be IgM or IgG.

Answer 26

Alloanti-I

Question 27

• Uncommon antibody, but can be found in: • Epstein-Barr virus (EBV) infection (infectious mononucleosis). • Asian individuals with congenital cataracts. • Can be IgM or IgG

Answer 27

Anti-i

Question 28

Laboratory Testing for Ii Antibodies Test Condition Effect on Ii Antibodies Pre-warming the test Enzyme treatment (ficin, papain)

Answer 28

Eliminates reactivity of insignificant anti-I (avoids cold agglutination). Enhances detection of anti-I and anti-i.

Question 29

Anti-I is associated with:

Answer 29

• Cold Agglutinin Disease (CAD) • Mycoplasma pneumoniae infection

Question 30

Anti-i is associated with:

Answer 30

• Infectious mononucleosis (Epstein-Barr virus) • Congenital cataracts (seen in Asians with the rare adult i phenotype)

Question 31

i Antigen is increased in disorders of RBC maturation, including:

Answer 31

• Dyserythropoiesis (abnormal RBC development) • Acute leukemia • Hypoplastic anemia • Megaloblastic anemia • Sideroblastic anemia • Thalassemia • Paroxysmal nocturnal hemoglobinuria (PNH) • Sickle cell disease • Chronic hemolytic anemia