Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Transfusion Science > L.11 HLA System > Flashcards

L.11 HLA System Flashcards

1
Q

What is the HLA system?

A

A complex of genes involved in the immune system’s ability to distinguish self from non-self.

Known as the Major Histocompatibility Complex (MHC) in humans.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where is the HLA system located?

A

On chromosome 6 (short arm, region 6p21).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the primary purpose of the HLA system?

A

Central to tissue compatibility, especially in:
* Organ and stem cell transplantation
* Platelet transfusions
* Disease association studies
* Autoimmune disorders
* Pharmacogenetics and immunogenetics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Who discovered the HLA system and when?

A

Discovered in 1954 by Jean Dausset.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What historical observation led to the discovery of the HLA system?

A

Certain patients developed leukoagglutinins following multiple transfusions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How polymorphic is the HLA complex?

A

Highly polymorphic, with each gene having many different alleles.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the three classes of proteins encoded by the HLA complex?

A
  • Class I: HLA-A, HLA-B, HLA-C
  • Class II: HLA-DR, HLA-DQ, HLA-DP
  • Class III: Genes involved in complement proteins and cytokines, but not classical HLA molecules.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the genes associated with HLA Class I molecules?

A

HLA-A, HLA-B, HLA-C.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where are HLA Class I molecules expressed?

A

All nucleated cells and platelets.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the function of HLA Class I molecules?

A

Present endogenous (intracellular) antigens to CD8+ cytotoxic T-cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a notable feature of HLA Class I molecules?

A

Extremely diverse polymorphism, e.g., HLA-A01, HLA-A02.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What clinical relevance do HLA Class I molecules have?

A

Transplantation compatibility, platelet refractoriness, disease associations.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the genes associated with HLA Class II molecules?

A

HLA-DR, HLA-DQ, HLA-DP.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Where are HLA Class II molecules primarily expressed?

A

On antigen-presenting cells (APCs): B cells, dendritic cells, macrophages.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the function of HLA Class II molecules?

A

Present exogenous (extracellular) antigens to CD4+ helper T-cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the clinical relevance of HLA Class II molecules?

A

Autoimmune diseases, graft-versus-host disease (GVHD), HLA-typing for bone marrow/stem cell transplantation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How are HLA genes inherited?

A

HLA genes are inherited as haplotypes, one from each parent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How many HLA haplotypes does each person have?

A

Each person has two HLA haplotypes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the chance that siblings are HLA identical?

A

Siblings have a 25% chance of being HLA identical

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What does the nomenclature HLA-A*02:01 represent?

A
  • ‘A’: locus
  • ‘02’: allele group
  • ‘01’: specific allele
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What has largely replaced older serologic designations in HLA typing?

A

Molecular nomenclature using DNA sequencing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is serologic typing?

A

An early method using antisera to detect HLA antigens on lymphocytes, now largely obsolete

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the gold standard method for high-resolution HLA typing?

A

SBT (Sequence-Based Typing)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What does NGS stand for in HLA typing advances?

A

Next-Generation Sequencing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What is one clinical application of HLA testing in organ transplantation?
Matching Class I and Class II HLA antigens improves graft survival
26
What can cause rejection in organ transplantation related to HLA?
Donor-specific antibodies (DSA) against HLA antigens
27
What is required for high-resolution matching in stem cell/bone marrow transplants?
Matching at HLA-A, -B, -C, -DRB1, and sometimes -DQB1
28
What can cause refractoriness in platelet transfusion?
Anti-HLA antibodies
29
What is the association of HLA-B27?
Ankylosing spondylitis
30
What diseases are associated with HLA-DR3/DR4?
Type 1 diabetes mellitus
31
What is the association of HLA-DQ2/DQ8?
Coeliac disease
32
HLA-B*57:01 is associated with hypersensitivity to _______.
abacavir
33
HLA-B*15:02 is associated with the risk of _______ with carbamazepine.
Stevens-Johnson Syndrome
34
What is the clinical application of HLA testing in Haematopoietic Stem Cell Transplantation (HSCT)?
High-resolution HLA matching critical for graft success ## Footnote Graft success in HSCT is significantly enhanced by ensuring high-resolution compatibility between donor and recipient HLA types.
35
How does HLA typing minimize rejection risk in solid organ transplants?
Pre-transplant HLA typing minimizes rejection risk ## Footnote HLA typing before organ transplantation helps match donor and recipient, reducing the likelihood of the recipient's immune system rejecting the transplanted organ.
36
In what situation are HLA-matched platelets used?
HLA-matched platelets used in patients with anti-HLA antibodies ## Footnote Patients who have developed antibodies against HLA may experience platelet refractoriness, making HLA-matching crucial for effective transfusions.
37
Provide an example of a disease associated with specific HLA types.
HLA-DQ2/DQ8 in coeliac disease ## Footnote The presence of certain HLA types, such as DQ2 and DQ8, is strongly linked to the predisposition for developing coeliac disease.
38
What are some other uses of HLA testing? List them.
Other uses include: * Paternity testing * Anthropological genetics ## Footnote HLA testing has applications beyond medical transplants, including determining biological relationships and studying genetic diversity in populations.
39
What does HLA typing evaluate?
Compatibility between donors and recipients ## Footnote HLA typing is essential in transplantation to ensure that the donor's and recipient's immune systems can coexist without rejection.
40
What is pre-sensitisation and what can it lead to?
Pre-sensitisation can lead to: * Hyperacute rejection in transplants * Platelet refractoriness in transfusions ## Footnote Previous exposure to HLA antigens can sensitize patients, making them more likely to reject future transplants or transfusions.
41
Which class of HLA antibodies is particularly noted in sensitised patients?
Anti-HLA antibodies, especially to Class I (e.g., anti-HLA-B8) ## Footnote Class I HLA antibodies are often formed in sensitised patients, complicating transplant procedures.
42
What is co-dominant inheritance in HLA genetics?
Both alleles at each locus are expressed ## Footnote This means that an individual will express both HLA alleles inherited from each parent, contributing to the diversity of HLA types.
43
Define haplotypes in the context of HLA genetics.
Inherited sets of HLA genes on a single chromosome ## Footnote Haplotype refers to the combination of alleles at multiple loci that are inherited together, such as HLA-A1, B8, DR3.
44
What is a genotype in HLA genetics?
Full set of HLA alleles from both parents ## Footnote The genotype provides a complete profile of an individual's HLA types, influencing transplant compatibility and disease susceptibility.
45
What is the crossover rate in the HLA region?
Less than 1% recombination in HLA region ## Footnote This low crossover rate means that HLA haplotypes are usually inherited intact, preserving the genetic association between alleles.
46
What is linkage disequilibrium?
Non-random association of specific alleles at different loci ## Footnote This phenomenon is important for understanding the genetic architecture of HLA and its implications in disease associations.
47
How does linkage disequilibrium affect transplant compatibility predictions?
It affects transplant compatibility predictions ## Footnote Linkage disequilibrium can lead to more accurate predictions of compatibility based on HLA profiles, impacting transplant success rates.
48
True or False: Linkage disequilibrium explains frequent HLA-disease associations.
True ## Footnote The non-random association of alleles can clarify why certain HLA types are consistently found in individuals with specific diseases.
49
What influences the accuracy of serologic typing versus DNA typing?
Linkage disequilibrium influences accuracy ## Footnote Understanding linkage disequilibrium helps improve the reliability of different typing methods in determining HLA compatibility.
50
What are the Class I HLA molecules?
HLA-A, HLA-B, HLA-C ## Footnote Class I molecules are present on all nucleated cells and platelets.
51
What are the Class II HLA molecules?
HLA-DR, HLA-DQ, HLA-DP ## Footnote Class II molecules are expressed on antigen-presenting cells (APCs) such as B cells, dendritic cells, macrophages, and endothelial cells.
52
What is the structure of Class I HLA molecules?
Heavy chain (45 kDa) + β2-microglobulin (noncovalent) ## Footnote This structure allows for the presentation of endogenous peptides.
53
What is the structure of Class II HLA molecules?
Two similar-sized chains: α (33 kDa), β (28 kDa) ## Footnote This configuration is essential for presenting exogenous peptides.
54
What is the primary function of Class I HLA molecules?
Present endogenous peptides to CD8+ T-cells ## Footnote This is crucial for the cytotoxic response against infected or malignant cells.
55
What is the primary function of Class II HLA molecules?
Present exogenous peptides to CD4+ T-cells ## Footnote This function is vital for helper T-cell responses.
56
What is one critical function of the HLA system?
Adaptive immunity: Critical for T-cell recognition ## Footnote The HLA system plays a key role in the immune response by enabling T-cells to recognize antigens.
57
How does the HLA system contribute to self/non-self recognition?
Prevents autoimmune response ## Footnote The ability to distinguish self from non-self is essential for preventing autoimmune diseases.
58
What is the significance of high polymorphism in the HLA system?
Maximizes immune repertoire and disease resistance ## Footnote This diversity enhances the ability of the immune system to respond to various pathogens.
59
What is HLA sensitization?
From previous transfusions, pregnancy, transplants ## Footnote Sensitization can lead to immune reactions during subsequent transfusions.
60
What causes Febrile Non-Haemolytic Transfusion Reactions (FNHTRs)?
Anti-HLA antibodies destroy donor WBCs → release of pyrogens ## Footnote This reaction is characterized by fever and chills following transfusion.
61
What is platelet refractoriness?
Inadequate count rise due to anti-HLA antibodies ## Footnote This condition often requires the use of HLA-matched platelets for effective treatment.
62
What is TRALI?
Transfusion-Related Acute Lung Injury ## Footnote TRALI is linked to HLA antibodies in donor plasma and can cause severe respiratory distress.
63
What is the purpose of leucodepletion in transfusion medicine?
To reduce sensitisation and CMV risk ## Footnote Leucodepletion is a common practice in many countries to enhance transfusion safety.
64
Are HLA antibodies commonly implicated in acute or delayed hemolytic transfusion reactions (HTRs)?
Rarely ## Footnote Most HTRs are caused by other factors, not HLA antibodies.
65
Are HLA antibodies implicated in Hemolytic Disease of the Fetus and Newborn (HDFN)?
No ## Footnote HDFN is typically due to other immunological factors, not HLA antibodies.

Transfusion Science (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions