Uncommon Blood Group 2 Flashcards
Why is the Scianna blood group named “SC”?
It was named after the first antibody maker
What was the first Scianna antibody discovered?
Anti-Sm in 1962, which reacted with the Sm antigen
What were the first two Scianna antigens called?
• Scl (formerly Sm)
• Sc2 (formerly Bu)
When was the Scianna blood group officially named?
1974
What high-prevalence antibody was found in the Marshall Islands in 1980?
Anti-Sc3
Where is the SC gene (ERMAP) located?
Chromosome 1p34
What protein does the Scianna gene code for?
Erythroid membrane-associated protein (ERMAP) (an RBC adhesion protein)
What are the major Scianna antigens?
- Sc1 and Sc2
- Sc4 (formerly Rd, low prevalence)
- Sc5 (STAR), Sc6 (SCER), Sc7 (SCAN) (high prevalence)
How do Scianna antigens react to enzymes?
• Resistant to ficin and papain
• Weakened by Dithiothreitol (DTT)
What type of immunoglobulin are Scianna antibodies?
IgG
When do Scianna antibodies react?
At AHG phase
Do Scianna antibodies cause Hemolytic Transfusion Reactions (HTRs)?
No
Do Scianna antibodies cause Hemolytic Disease of the Fetus and Newborn (HDFN)?
Yes, but mild
Why is the Dombrock blood group named “Do”?
It was named after the first antibody maker, Mrs. Dombrock
What was the first Dombrock antibody discovered?
Anti-Doa in 1965
When was Anti-Dob discovered?
1973
What is the relationship between Doa and Dob?
Dob is the antithetical antigen to Doa
Where is the Dombrock gene (ART4) located?
Chromosome 12p12.3
What differentiates Doa and Dob genetically?
They differ in three nucleotide positions
What amino acid is present in Doa at position 265?
Aspartic acid
What amino acid is present in Dob at position 265?
Asparagine
What type of protein carries Doa and Dob?
Mono-ADP-ribosyltransferase 4 (GPI-anchored)
Are Doa and Dob strong immunogens?
No, they are weak immunogens
What are the high-prevalence antigens in the Dombrock system?
Gy(a) (Gregory), Hy (Holley), and Jo(a) (Joseph)
What amino acid is found in the Hy antigen at position 108?
Glycine
What amino acid is found in the Jo(a) antigen at position 117?
Threonine
How do Dombrock antigens react to enzymes?
• Resistant to Ficin, Papain, Glycine-EDTA
• Sensitive to Dithiothreitol (DTT)
What type of immunoglobulin are Dombrock antibodies?
IgG
Are Dombrock antibodies common?
No, they are rare
What transfusion reaction can Dombrock antibodies cause?
Delayed Hemolytic Transfusion Reactions (HTRs)
Can Dombrock antibodies cause HDFN?
Yes, but mild
When do Dombrock antibodies react?
At Direct Antiglobulin Test (DAT)
Who was the Cartwright blood group named after?
The first antibody maker, Cartwright, in 1956
What are the three Cartwright phenotypes?
• Yt(a+b-)
• Yt(a+b+)
• Yt(a-b+)
Where is the AChE gene (Cartwright blood group gene) located?
Chromosome 7q22
What causes the difference between Yt(a) and Yt(b)?
A single nucleotide mutation at position 353
What amino acid is found in Yt(a)?
Histidine
What amino acid is found in Yt(b)?
Asparagine
What enzyme does the Cartwright antigen associate with?
Acetylcholinesterase (AChE)
How do Cartwright antigens react to enzymes?
• Sensitive (variable) to ficin, papain, Dithiothreitol (DTT)
• Resistant to glycine-acid EDTA
Are Cartwright antigens well developed at birth?
Yes
What disorder results in the absence of Cartwright antigens?
Paroxysmal Nocturnal Hemoglobinuria (PNH)
What is Paroxysmal Nocturnal Hemoglobinuria (PNH)?
An acquired hematopoietic stem cell disorder caused by a deficiency in GPI-linked proteins
What type of antibodies are Cartwright (Yt) antibodies?
IgG, stimulated by pregnancy or transfusions
What are the two Cartwright antibodies and their immunogenicity
- Anti-Yta – Highly immunogenic, can cause hemolytic transfusion reactions (HTRs)
- Anti-Ytb – Weakly immunogenic
What is unique about the Chido-Rodgers blood group?
It is the only blood group associated with a complement protein (C4).
What are the two isoforms of the C4 glycoprotein and their associated antigens
- C4B – Carries Chido (Ch) antigens
- C4A – Expresses Rodgers (Rg) antigens
Where are the genes coding for C4A and C4B located?
Chromosome 6p21.3
What are the prevalence rates of Ch and Rg antigens in most populations?
• Ch: 96-98%
• Rg: 97-98%
How are Chido-Rodgers antibodies identified?
Neutralization with pooled plasma
How do Chido-Rodgers antigens react to enzymes and chemicals?
• Destroyed by: Ficin & Papain
• Resistant to: Dithiothreitol (DTT) & Glycine-acid EDTA
Are Chido-Rodgers antibodies clinically significant?
No, they are weakly reacting and not significant.
How did the Colton blood group get its name?
A misreading of “Calton” due to poor handwriting in 1967.
What gene codes for the Colton antigen?
Aquaporin 1 (AQP1) gene
Where is the AQP1 gene located?
Chromosome 7p14
What protein carries Colton antigens?
Aquaporin 1 (AQP1), an integral membrane protein
Are Colton antigens present at birth?
Yes, they are fully developed on newborns.
How do Colton antigens react to enzyme treatments?
They are resistant to Ficin, Papain, Chloroquine, and Dithiothreitol (DTT)
What are the four Colton antigens and their prevalence?
• Coa – Highly prevalent
• Cob – Low prevalence (found in ~10% of most populations)
• Co3 – Present in all RBCs except the rare Co(a-b-) phenotype
• Co4 – A highly prevalent antigen found in some Co(a-b-) individuals
What type of antibodies are Colton antibodies?
Usually IgG, enhanced with enzyme-treated RBCs
What are the clinical significances of Colton antibodies?
• Anti-Coa – Causes HTR and HDFN
• Anti-Cob – Appears with other specificities and causes HTR and HDFN
• Anti-Co3 – Causes severe HDFN
How did the Knops blood group get its name?
Named after Mrs. Knops, the first antibody maker.
How many antigens are in the Knops blood group, and where are they located?
9 antigens located on Complement Receptor 1 (CR1)
Where is the CR1 gene located?
Chromosome 1q32
What are the antithetical pairs in the Knops blood group?
• Kna / Knb
• McCa / McCb
• Sla / Vil
How do Knops antigens react to enzyme and chemical treatments?
• Destroyed by: Ficin, Papain, and Dithiothreitol (DTT)
• Resistant to: Glycine-acid EDTA
What type of antibodies are Knops antibodies?
IgG, reacting at AHG phase
Do Knops antibodies cause HDFN or HTR?
No, they are not clinically significant.
Who is most likely to develop Anti-Kna?
Individuals with multiple transfusions.
Which Knops antibody is commonly found in Black populations?
Anti-Sla
Why is the Indian blood group named “Indian”?
It was named after the first individuals found with the antigen, who were from India.
What molecule carries Indian blood group antigens?
CD44 adhesion molecule
Where is the CD44 gene located?
Chromosome 11p13
What are the two main antigens of the Indian blood group, and which is more common?
• Ina – Low prevalence (found in 4% of Indians, 11% of Iranians, 12% of Arabs)
• Inb – High prevalence (antithetical to Ina)
How do Indian antigens react to enzyme and chemical treatments?
• Destroyed by: Ficin, Papain, and Dithiothreitol (DTT)
• Resistant to: Glycine-acid EDTA
What type of antibodies are Indian antibodies?
Usually IgG, reacting at AHG phase
Do Indian antibodies bind complement?
No, they do not bind complement.
What clinical significance do Indian antibodies have?
They cause immediate HTR but do not cause HDFN.
Who was the Gerbich blood group named after, and when?
Named after Mrs. Gerbich in 1960, became a system in 1990.
How many high-prevalence and low-prevalence antigens are in the Gerbich blood group?
6 high-prevalence antigens, 5 low-prevalence antigens
What glycoproteins carry Gerbich antigens?
Glycophorin C (GPC) and Glycophorin D (GPD)
What role do GPC and GPD play in RBC function?
They help maintain RBC membrane stability by interacting with protein band 4.1 and contribute to the net negative charge of RBCs.
Where is the GYPC gene located? (gerbich)
Chromosome 2q14.3
How many copies of Glycophorin C and D are present per RBC?
• Glycophorin C (GPC): 135,000 copies
• Glycophorin D (GPD): 50,000 copies
How does the Gerbich phenotype affect Kell antigen expression?
RBCs with Gerbich or Leach phenotypes have weak Kell antigen expression.
What type of antibodies are Colton antibodies?
Usually IgG, enhanced with enzyme-treated RBCs
What are the clinical significances of Colton antibodies?
• Anti-Coa – Causes HTR and HDFN
• Anti-Cob – Appears with other specificities and causes HTR and HDFN
• Anti-Co3 – Causes severe HDFN
Who was the Diego blood group named after?
Named after the first antibody maker from a Venezuelan family during an HDFN investigation.
How many antigens are in the Diego blood group system?
22 antigens (3 sets of antithetical pairs + 17 low-prevalence antigens).
What RBC membrane protein carries Diego antigens?
Band 3 (a.k.a. Red Cell Anion Exchanger or Solute Carrier Family 4)
How many copies of Band 3 are present per RBC?
Approximately 1 million copies per RBC
What is the role of Band 3 in RBCs?
• Crosses the RBC membrane multiple times.
• Both amino- and carboxyl-terminal domains face the cytoplasm.
• Interacts with ankyrin and protein 4.2, stabilizing the RBC membrane skeleton.
What gene encodes Diego antigens, and where is it located?
SLC4A1 gene, located on chromosome 17q21-q22.
What is the prevalence of the Dia antigen?
• Rare in most populations.
• More common in Mongoloid ancestry (54% in South American Indians).
What type of antibodies are Diego antibodies?
Usually IgG (sometimes IgM), reacting at IAT (Indirect Antiglobulin Test).
Can anti-Dia and anti-Dib cause clinical issues?
Yes, both can cause HDFN and HTR.
