Platelet Antigens Flashcards
Function of:
GPIIb/IIIa
Integrin that binds fibrinogen post activation resulting in platelet aggregation and formation of the platelet plug
Function of:
GPIb/V/IX
vWF receptor
Facilitates adhesion to the subendothelium after vascular injury and initiates signaling events leading to platelet activation
Function of:
GPIa/IIa
Collagen receptor
Function of:
GPIV/CD36
Class B scavenger receptor. Binds a bunch of things including LDL, thrombospondin, types 1 and 4 collagen, and malaria infected RBCs
Function of:
GPVI
Member of Ig superfamily
Collagen receptor- interactions with collagen exposed on extra cellular matrix result in platelet activation
Disorder resulting in missing GPIIb/IIIa
Glanzmann thrombasthenia
Serious bleeding problems
Disorder resulting in missing GPIb/V/IX
Bernard Soulier syndrome
- prolonged bleeding time
- thrombocytopenia
- presence of giant platelets
Location of HPA-1a/1b
GPIIIa
Frequency of HPA-1a/1b
72% a/a
26% a/b
2% b/b
Location HPA-4a/4b
GPIIIa
Location HPA-3a/3b
GPIIb
Other GPIIb/IIIa HPAs that are low frequency but more common than just 1 family
HPA-6bw (1%)
HPA-21bw(2%)
Frequency in Japanese populations
Frequency HPA3a/3b
37% a/a
48% a/b
15% b/b
Location of HPA-2a/2b
GPIb(alpha)
Location HPA-12bw
GPIb(beta)
Location HPA-5a/5b
GPIa
Location HPA-15
CD109
Location of most ABO antigens on platelets
GPIIb and PECAM-1
A2 expression on platelets
A2 individuals do not express detectable A antigen on their platelets
Other RBC antigens present of platelets
Lea, Leb, I, i, P, Pk, Cromer
Other platelet antigens that aren’t HPAs but can be platelet antibody targets
GPIV/CD36- antibodies cause FNAIT, PTP, txn refractoriness
GPVI- mild autoimmune thrombocytopenia
GPVI autoantibodies
Induce shedding of GPVI from platelet leading to to reduced collagen binding and clinically significant bleeding
HLA on platelets
Express Class I
Significant amounts of HLA-A and HLA-B (minimal C)
HLA match grade for platelets
A
4 antigen match
HLA match grade for platelets
B1U
3 antigen match
1 antigen unknown/blank
HLA match grade for platelets
B1X
3 antigen match
1 crossreactive group
HLA match grade for platelets
B2UX
2 antigen match
1 antigen unknown/blank
1 cross reactive group
HLA match grade for platelets
C
1 mismatched antigen
HLA match grade for platelet
D
2 or more mismatched antigens
HLA match grade for platelets
R
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