Duffy

Question 1

What chromosome is FY gene located on?

Answer 1

Chromosome 1
Syntenic to Rh
Far enough away that Rh and Duffy are not linked

Question 2

What is the gene name for FY?

Answer 2

DARC

Duffy antigen receptor for cytokines

Question 3

What antigens are present if FY*01 is present?

Answer 3

Fya, Fy3, Fy5, Fy6,

Question 4

What antigens are present if FY*02 is present?

Answer 4

Fyb, Fy3, Fy5, Fy6

Question 5

What antigens are present if FYmod is present?

Answer 5

Fy Mod phenotype called Fyx
Reduced expression of Fyb antigens
Caused by SNP 
Occurs in White population
May require adsorption/elution

Question 6

What antiges are present if FY01N or FY02N is present?

Answer 6

FY null = no Fy antigens

Present in Blacks

Question 7

What is the frequency of Fya in Japanese?

Answer 7

96% are Fya+

Question 8

What is the frequency of Fy(a-b-) in whites and blacks?

Answer 8

Very rarely occurs in whites
67% of blacks are Fy(a-b-)
- also lack Fy3 and Fy5

Question 9

What is the frequency of Fya in Whites and blacks?

Answer 9

66% of whites are positive

13% of blacks are positive

Question 10

What is frequency of Fyb in Whites and Blacks?

Answer 10

83% of whites are positive

23% of blacks are positive

Question 11

What are the characteristics of Duffy antigens?

Answer 11

Well developed on cord cells
Destroyed by enzymes and ZZAP (contains enzyme)
Not affected by DTT

Question 12

At what gestation can Duffy antigens be detected?

Answer 12

As early as 6 weeks

Question 13

Where are Duffy antigens found?

Answer 13

Found in tissues through out the body such as the brain, lung, spleen, thyroid, thymus, and kidney

Question 14

What are the characteristics of anti-Fya and anti-Fyb?

Answer 14

Mostly IgG1
Shows dosage
Anti-Fya is common in Whites
- Anti-Fya is 3x more common than anti-K
Causes HDFN and TRN TRX
Enhanced by LISS

Question 15

What is Fy3?

Answer 15

High freq. present when either Fya or Fyb is present
not destroyed by enzymes (located further down protein)
Anti-Fya is usually formed first, then Fy3

Question 16

What is Fy5?

Answer 16

Hgh freq present when Rh antigens are present and with Fya or Fyb.
Not expressed on Rh null cells regardless of Fya or Fyb expression.
Not destroyed by enzymes
Weak on Fyx and D– cells

Question 17

What is Fy6?

Answer 17

an antigen defined by a murine monoclonal antibody
No human anti-Fy6 has been found
Absent on Fy3 negative and Fy5 negative cells
Destroyed by enzymes

Question 18

What is FYmod?

Answer 18

Fyx is phenotype not an antigen
Weak Fyb caused by SNP in Exon 2
Found in white people
May required adsorpt/elution to detect
monoclonal anti-Fyb may detect

Question 19

What is the Fynull phenotype?

Answer 19

Mutation results in Fy gene that produces no DARC antigen on RBC’s
Homozygotes will have Fy(a-b-,3-5-)
Common in Blacks

Question 20

What is Fy(a-b-) found in European popuation?

Answer 20

Very, very rare
Mutation on DARC gene affects Fy on all tissues
Can make anti-Fy3

Question 21

What is GATA-1?

Answer 21

mutation caused by a SNP in the GATA region of the Fyb gene blocks mRNA trasnscription in RBC’s only
GATA is resposible for Fy gene in blacks Fy(a-b-)
70% of blacks are Fy(a-b-)
Unlikely to make anti-Fy3 or anti-Fy5 because Fyb is present in tissues

Question 22

Characteristics of Anti-Fy3?

Answer 22

Can form in African Fy(a-b-) in multiply transfused patients. This antibody is negative with cord cells and directed against subtle difference in DARC on RBC’s then DARC on tissues
Anti-Fy3 formed in Caucasians will react with cord cells

Question 23

Characteristics of Anti-Fy5?

Answer 23

All examples were seen in african Fy(a-b-) individuals

Will not react with Rh null cells and reacts weakly with D– cells

Question 24

Describe the structure of Fy antigen?

Answer 24

Multipass protein that pass membrane 7X
Fya, Fyb, and Fy6 are located on N terminus and destroyed by enzymes
Fy3 and Fy5 are on the 3rd loop and not affected y enzymes

Question 25

How can you use Duffy genotyping?

Answer 25

Genotype recently transfused patients
Determine if apparent Fy(b-) are actually Fyx
Determine if cells are double dose
Use for malaria and genetic studies
Determine which Fy(a-b-) carry Gata-1 mutation and can receive Fyb positive units

Question 26

What is the function of DARC?

Answer 26

Functions as a scanvenger and removes unwanted cytokines like IL-8
It is a receptor for P. vivax and P. knowlesi

Question 27

What are the markers for African ancestry?

Answer 27

Ro (Dce), V+, Jsa+, Le(a-b-), Fy(a-b-) Jk(a+b-), S-s-U-