Platelet Antigens

Question 1

Function of:

GPIIb/IIIa

Answer 1

Integrin that binds fibrinogen post activation resulting in platelet aggregation and formation of the platelet plug

Question 2

Function of:

GPIb/V/IX

Answer 2

vWF receptor
Facilitates adhesion to the subendothelium after vascular injury and initiates signaling events leading to platelet activation

Question 3

Function of:

GPIa/IIa

Answer 3

Collagen receptor

Question 4

Function of:

GPIV/CD36

Answer 4

Class B scavenger receptor. Binds a bunch of things including LDL, thrombospondin, types 1 and 4 collagen, and malaria infected RBCs

Question 5

Function of:

GPVI

Answer 5

Member of Ig superfamily

Collagen receptor- interactions with collagen exposed on extra cellular matrix result in platelet activation

Question 6

Disorder resulting in missing GPIIb/IIIa

Answer 6

Glanzmann thrombasthenia

Serious bleeding problems

Question 7

Disorder resulting in missing GPIb/V/IX

Answer 7

Bernard Soulier syndrome

• prolonged bleeding time
• thrombocytopenia
• presence of giant platelets

Question 8

Location of HPA-1a/1b

Answer 8

GPIIIa

Question 9

Frequency of HPA-1a/1b

Answer 9

72% a/a
26% a/b
2% b/b

Question 10

Location HPA-4a/4b

Answer 10

GPIIIa

Question 11

Location HPA-3a/3b

Answer 11

GPIIb

Question 12

Other GPIIb/IIIa HPAs that are low frequency but more common than just 1 family

Answer 12

HPA-6bw (1%)
HPA-21bw(2%)

Frequency in Japanese populations

Question 13

Frequency HPA3a/3b

Answer 13

37% a/a
48% a/b
15% b/b

Question 14

Location of HPA-2a/2b

Answer 14

GPIb(alpha)

Question 15

Location HPA-12bw

Answer 15

GPIb(beta)

Question 16

Location HPA-5a/5b

Answer 16

GPIa

Question 17

Location HPA-15

Answer 17

CD109

Question 18

Location of most ABO antigens on platelets

Answer 18

GPIIb and PECAM-1

Question 19

A2 expression on platelets

Answer 19

A2 individuals do not express detectable A antigen on their platelets

Question 20

Other RBC antigens present of platelets

Answer 20

Lea, Leb, I, i, P, Pk, Cromer

Question 21

Other platelet antigens that aren’t HPAs but can be platelet antibody targets

Answer 21

GPIV/CD36- antibodies cause FNAIT, PTP, txn refractoriness

GPVI- mild autoimmune thrombocytopenia

Question 22

GPVI autoantibodies

Answer 22

Induce shedding of GPVI from platelet leading to to reduced collagen binding and clinically significant bleeding

Question 23

HLA on platelets

Answer 23

Express Class I

Significant amounts of HLA-A and HLA-B (minimal C)

Question 24

HLA match grade for platelets

A

Answer 24

4 antigen match

Question 25

HLA match grade for platelets

B1U

Answer 25

3 antigen match

1 antigen unknown/blank

Question 26

HLA match grade for platelets

B1X

Answer 26

3 antigen match

1 crossreactive group

Question 27

HLA match grade for platelets

B2UX

Answer 27

2 antigen match
1 antigen unknown/blank
1 cross reactive group

Question 28

HLA match grade for platelets

C

Answer 28

1 mismatched antigen

Question 29

HLA match grade for platelet

D

Answer 29

2 or more mismatched antigens

Question 30

HLA match grade for platelets

R

Answer 30

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