Lecture 6: MHC Binding

Question 1

What is required for a naive T cell to be activated?

Answer 1

1. recognize the Ag at the TCR

2. binding of co-stimulatory and co-receptors

Question 2

What process occurs once a T cell is activated?

Answer 2

1. undergoes clonal expansion

Question 3

What does Th1 cells do?

Answer 3

1. release IFN-gamma to activate tissue macrophages
   - -rid intracellular microbes
2. develop cytotoxic T cells

Question 4

What do Th2 cells do?

Answer 4

1.help B cells proliferate into memory and plasma cells

Question 5

What is secreted by Th2 to help B cell proliferation?

Answer 5

1. IL-4

Question 6

What does IL-4 do?

Answer 6

1. secreted from Th2 cells to help B cell proliferate into memory and plasma cells

Question 7

What is the TCR, found at the membrane, made of?

Answer 7

1. alpha chain and beta chains

2. both form constant and variable regions

Question 8

What is the Ag-binding site formed of?

Answer 8

1. the constant and variable regions of the alpha, beta chains

Question 9

Can T cells express gamma and delta chains on the TCR?

Answer 9

yes, poor understanding

Question 10

What is known about the specificity of the gamma, and delta chain TCRs?

Answer 10

1. broad specificity

2. bind to HSP and phospholipid Ag

Question 11

What is the molecular weight of alpha chains in TCR?

Answer 11

1. 50kDa

Question 12

What is the molecular weight of beta chains in TCR?

Answer 12

1. 39kDa

Question 13

What is the location of the constant and variable regions on the TCR?

Answer 13

1. constant region, located near the PM so it will always bind to the T cell
2. variable regions is presented to the Ag binding site to provide different attachments for different Ag

Question 14

What is CD3 and why is it significant to TCR?

Answer 14

1. signaling complex of gamma, delta, espilon chains
2. acts to help with APC presentation/binding to MHC
3. therefore is a co-receptor to activate T cells

Question 15

Th cells are restricted to recognizing peptides presented on what MHC class?

Answer 15

MHC II on the APC

Question 16

Tc cells are restricted to killing cells presented on what MHC class?

Answer 16

MHC I

Question 17

What type of Ag is able to bind peptides and is critical for Ag presentation?

Answer 17

human leukocyte Ag (HLA)

Question 18

What are human leukocyte Ag (HLA)?

Answer 18

polymorphic genes that are the human equivalent of MHC class I and class II

Question 19

Which class of HLA is expressed on all nucleated cells?

Answer 19

MHC class I

Question 20

HLA-A, HLA-B, HLA-C are all ___________

Answer 20

MHC class I genes that encode a polymorphic heavy chain

Question 21

What do the polymorphic heavy chains of class I HLA genes combine with?

Answer 21

Beta2-microglobulin

Question 22

What is the code for MHC class II human leukocyte antigen (HLA)?

Answer 22

-DP, -DR, -DQ

Question 23

Do MHC class II HLA genes contribute to peptide-binding groove?

Answer 23

yes, with use of alpha and beta chains

Question 24

How long is the amino acid sequence that MHC class I regions can bind? And MHC II?

Answer 24

1. 8 to 10

2. 10 to 20

Question 25

In MHC class I, the peptide binding cleft is formed by______?

Answer 25

the polymorphic alpha chain, which also provides attachment to the PM

Question 26

In MHC class II, the peptide binding cleft is formed by __________?

Answer 26

both the alpha 1 and beta 1 complex units

Question 27

Which cells express MHC class I?

Answer 27

all nucleated cell

Question 28

Which cells express MHC II?

Answer 28

- DC - Mononuclear phagocytes - B lymph - endothelium cells - thymic epithelium

Question 29

Peptide antigens that bind with MHC I molecules come from where and use what process to make it to this point?

Answer 29

1. come from viruses that infect host cells | 2. use endogenous pathway

Question 30

If a peptide Ag were to bind with MHC II, where is this Ag taken up from and what TCR interacts with it?

Answer 30

1. taken up from environment via exogenous pathway | 2. interacts with CD4+ T cells

Question 31

What effect will a Dendritic cell have on a Naive T cell if an Ag is presented?

Answer 31

The naive T cell will be activated, undergo clonal expansion, and differentiate into effector T cells

Question 32

Effector T cell binds with a macrophage, what is the end result?

Answer 32

The macrophage is activated and thus begins cell mediated immunity

Question 33

What happens if a B cell, with antigen, interacts with an effector T cell?

Answer 33

Causes B cell activation that produces antibodies, and therefore a humoral response.

Question 34

What ports of entry allows a microbial Ag to be transported to the regional lymph nodes?

Answer 34

1. entrance via the skin 2. the GI 3. Respiratory tract - -DC capture and transport them to regional LN

Question 35

What port of entry causes microbial Ag to be transported to the spleen?

Answer 35

Ag that enter the bloodstream

Question 36

Ag that enter the blood stream, and encounter APC, are transported where>

Answer 36

the spleen

Question 37

Ag the enter via the skin, GI, or respiratory tracts, or other mucosal tracts except the eye are transported where?

Answer 37

To regional lymph nodes

Question 38

What is IFN-gamma able to produce?

Answer 38

stimulates the MHC II expression and increases activation of CD4+ cells

Question 39

What compounds are able to activate MHC I, and therefore activation of CD8+ T cells?

Answer 39

IFN-gamma and Type I interferons

Question 40

What is HLA-DM?

Answer 40

provides the most relevant Ag for the APC to present

Question 41

What are the 3 functions of HLA-DM?

Answer 41

1. dissociates CLIP from the peptide binding groove of MHC II 2. Stabilizes and prevents degradation of empty MHC II 3. Helps binding of Ag fragments to the binding groove

Question 42

Draw out the pathways for MHC I and MHC II uptake and processing of microbe

Answer 42

yes

Question 43

Are DC able to present Ag via MHC I pathways?

Answer 43

yes this is cross presentation

Question 44

What is the process of cross presentation?

Answer 44

1. infected host cell is taken up by DC 2. The viral Ag enters the DC cytosol 3. MHC I are bound with the viral Ag peptide 4. this is presented to CD8 cells with a costimulator 5. T cells generate effector response

Question 45

What is an immunodominant peptide?

Answer 45

Any of the peptides having a strong affinity for binding with class I or II histocompatibility antigens and for stimulating a response by T lymphocytes.

Question 46

How are immunodominant peptides produced and what are the benefits of them?

Answer 46

Immunodominant peptides are produced by antigen processing, are expressed on the surface of macrophages and other antigen-presenting cells, and may be useful both in desensitizing people to allergens and in vaccine production.