Immunopathology - Week 10 - Antigen Presentation and MHC

Question 1

A substance that has the ability to provoke an immune response is known as?

Answer 1

An antigen.

Question 2

What does MHC stand for?

Answer 2

Major Histocompatibility Complex.

Question 3

How do T cells see antigens?

Answer 3

T cells only recognise Ag when presented in the context of self Major Histocompatibility Complex. It distinguishes B and T cell recognition.

Question 4

What does APC stand for?

Answer 4

Antigen presenting cell.

Question 5

What type of cell mediate the cellular immune response and ‘presents’ antigen to the cells that will deal with antigen?

Answer 5

Antigen presenting cell.

Question 6

List three examples of Antigen presenting cells (APC).

Answer 6

1. Dendritic cells
2. Macrophages
3. B lymphocytes

Question 7

Describe the process of Antigen presentation.

Answer 7

• External threat is eaten by the antigen presenting cell.
• Antigen presenting cell presents antigen to the helper T cell.

Question 8

A group of genes that encode cell surface proteins essential for the immune system to recognize and respond to foreign antigens is known as?

Answer 8

Major Histocompatibility Complex (MHC).

Question 9

In humans, MHC is referred to as…?

Answer 9

Human Leukocyte Antigen (HLA).

Question 10

What does HLA stand for?

Answer 10

Human Leukocyte Antigen.

Question 11

In humans, where is the HLA located?

Answer 11

Chromosome 6.

Question 12

Presenting antigenic peptides to T lymphocytes, initiating an adaptive immune response is a function of what?

Answer 12

MHC molecules.

Question 13

List the 2 types of MHC.

Answer 13

1. MHC class I
2. MHC class II

Question 14

What is MHC Class I composed of?

Answer 14

Composed of one alpha chain and one beta-2 microglobulin.

Question 15

In MHC Class I, how many domains are in the alpha chain?

Answer 15

3 domains:
a1, a2, a3.

Question 16

In MHC Class I, the peptide-binding groove is located between?

Answer 16

a1 and a2.

Question 17

MHC Class I is found on the surface of?

Answer 17

All nucleated cells.

Question 18

Endogenous antigens (e.g, viral or intracellular proteins) are presented by?

Answer 18

MHC Class I.

Question 19

MCH Class I is recognised by?

Answer 19

CD8+ Cytotoxic T cells.

Question 20

Describe the pathway of MCH Class I.

Answer 20

• Pathogens are degraded by the proteasome
• Peptides are transported to the endoplasmic
  reticulum (ER) via TAP (Transporter
  Associated with Antigen Processing).
• Peptides are loaded onto MHC Class I
  molecules in the ER.
• The complex is transported to the cell
  surface

Question 21

What is MHC Class II composed of?

Answer 21

two chains (a and b).

Question 22

In MHC Class II, how many domains are in the two chains?

Answer 22

Two domains in each chain.
(a1, a2, b1, b2)

Question 23

In MHC Class II, the peptide-binding groove is located between?

Answer 23

a1 and b1.

Question 24

MHC Class II is found on?

Answer 24

Antigen presenting cells.

Question 25

Exogenous antigens (e.g., bacterial or extracellular proteins) are presented by?

Answer 25

MHC Class II.

Question 26

MCH Class II is recognised by?

Answer 26

CD4+ Helper T cells.

Question 27

Describe the pathway of MCH Class II.

Answer 27

* Extracellular antigens are endocytosed and degraded in endosomes/lysosomes. * MHC Class II molecules are synthesized in the ER and bound to the invariant chain (Ii) to prevent premature peptide binding. * In endosomes, the invariant chain is degraded, leaving CLIP (Class II- Associated Invariant Chain Peptide) in the groove. * HLA-DM facilitates the exchange of CLIP for the antigenic peptide. * The MHC-peptide complex is transported to the cell surface

Question 28

What are the two types of immunity involved in immune responses to fungal agents?

Answer 28

Innate immunity and adaptive immunity.

Question 29

Phagocytosis is a strong defense against what?

Answer 29

Fungi.

Question 30

What type of pathway of complement can clear fungal infection?

Answer 30

Lectin pathway

Question 31

What type of pathways enhance fungal clearance by phagocytosis?

Answer 31

Classical and alternate pathways.

Question 32

Immunity to bacteria is mainly achieved by what?

Answer 32

Antibodies.

Question 33

Antibodies provide immunity against bacteria by?

Answer 33

* Removing the bacteria * Neutralisation and/or inactivation of toxins

Question 34

Bacteria that are introduced in low numbers or are weakly pathogenic can be cleared by what?

Answer 34

Phagocytic cells.

Question 35

Bacteria that are introduced in high numbers or are strongly pathogenic can be cleared by?

Answer 35

An adaptive immune response.

Question 36

Immune responses to viral agents such as: * Induction of IFNα and IFNβ and activation of Natural Killer cells * Cytokines can be produced by macrophages, monocytes and fibroblasts * Cytokines induce an anti-viral state in surrounding cells * Cytokines also induce lytic activity in Natural Killer cells Are what sort of mechanism?

Answer 36

Non-specific mechanisms

Question 37

Immune responses to viral agents such as: * IgA prevents mucosal entry and re-infection * IgM, IgG and IgA prevent viral fusion to target cells * IgG enhances phagocytosis * IgM agglutinates viral particles * IgM and IgG activate the classical complement pathway * IFNγ has direct cytotoxic activity * Cytotoxic T cells kill virally infected cells * Natural Killer cells and macrophages kill infected cells Are what sort of mechanism?

Answer 37

Specific mechanisms.

Question 38

List three non-specific mechanism in immune responses to viral agents.

Answer 38

* Induction of IFNα and IFNβ and activation of Natural Killer cells * Cytokines can be produced by macrophages, monocytes and fibroblasts * Cytokines induce an anti-viral state in surrounding cells * Cytokines also induce lytic activity in Natural Killer Cells

Question 39

List three specific mechanism in immune responses to viral agents.

Answer 39

1. IgA prevents mucosal entry and re-infection 2. IgG enhances phagocytosis 3. Cytotoxic T cells kill virally infected cells 4. Natural Killer cells and macrophages kill infected cells