T cell Immunity Part 1

Question 1

What do CD8+ naive T cells turn into?

Answer 1

cytotoxic T lymphocytes

Question 2

What do CD4+ naive T cells turn into?

Answer 2

T helper lymphocytes

Question 3

What does each T cell express?

Answer 3

a TCR with a variable region specific to ONE UNIQUE PEPTICE

Question 4

What does the transmembrane region do for the TCR?

Answer 4

keeps TCR bound to the cell

Question 5

What can T cell receptors recognize?

Answer 5

antigens of protein origin

• antigen is a protein and epitopes a peptide = there are multiple epitopes in one antigen = pathogen have many proteins that can be recognize antigen

Question 6

What is the process of T cell antigen recognition?

Answer 6

1. epitopes recognized by T-cell receptors are often buried in protein
2. antigen must first be broken down into peptide fragments
3. epitope peptide binds to a self molecule (MHC)
4. T-cell receptor binds to a complex of MHC molecule and epitope peptide

Question 7

What are the two types of MHC - major histocompatibility complex?

Answer 7

MHC class I and MHC class II

Question 8

What is the role of MHC class I?

Answer 8

epitope peptide are 8-10 AA in length and from endogenous sources which are presented to CD8+ T cells

Question 9

What is the role of MHC class II?

Answer 9

epitope peptide are 13-18 AA in length and from exogenous sources which are presented to CD4+ T cells

– longer peptides creates “hot-dog bun” shape when epitope is bound to MHC class II

Question 10

What is the structure of MHC I molecules?

Answer 10

one large glycoprotein heavy chain + a small protein light chain

Question 11

What is the structure of MHC II molecules?

Answer 11

two nonidentical (trans)membrane bound glycoprotein chains and has a larger peptide-binding cleft

Question 12

What is necessary for MHC - TCR interactions to work?

Answer 12

antigenic epitopes recognized by T cells must be the correct associated MHC molecules to be recognized (no T cell activation)

Question 13

How do MHC-TCR interactions work?

Answer 13

T-cell co-receptor CD4/CD8 interacts on the side of the MHC molecule to to disrupt antigen binding site

Question 14

What receptors do CD4+ and CD8+ T-cels express?

Answer 14

CD4=helper T cells –> receptor: CD4

CD8+=cytotoxic T cells –> receptor: CD8

Question 15

What are super antigens?

Answer 15

proteins produced by pathogens that bind with HIGH affinity to MHC class II molecules on antigen presenting cells

Question 16

What does a superantigen do?

Answer 16

binds to membrane of MHC molecule cell

cross-link to T-cell receptors

intensely activates T cell and antigen presenting cell

Question 17

What does T cell activation by super antigens cause?

Answer 17

excessive production of cytokines (CD4 T cells)

cytokine storm

systemic toxicity

toxic shock syndrome toxin I

bacterial SA: binds to TCR and MHC class II

viral SA: binds to antigen-presenting cell

Question 18

What do t-cells target?

Answer 18

intracellular pathogens (viruses and cater that survive phagocytosis)

Question 19

Where are endogenous peptides from pathogens derived?

Answer 19

cytosolic: viruses and some bacteria

Question 20

Where are exogenous peptides from pathogens derived?

Answer 20

intravesicular: professional intracellular microbes that survived phagocytosis

Question 21

Where and how are cytosolic pathogens degraded?

Answer 21

cytosol by proteasome into smaller peptides

Question 22

What do cytosolic pathogen peptides bind to?

Answer 22

MHC class I

Question 23

What are cytosolic pathogen peptides presented to?

Answer 23

effector CD8 T cells

Question 24

What is the effect of cytosolic pathogens on the presenting cell?

Answer 24

cell death

Question 25

Where and how are intravesicular pathogens degraded?

Answer 25

endocytic vesicles (low pH) and degraded by endosomal and lysosomal enzymes

Question 26

What do intravesicular pathogen peptides bind to?

Answer 26

MHC class II

Question 27

What are intravesicular pathogen peptides presented to?

Answer 27

effector CD4 T cells

Question 28

What is the effect of intravesicular pathogens on the presenting cell?

Answer 28

activation of macrophage to kill intravesicular bacteria and parasites

Question 29

Once loaded onto MHC class I or II, where are antigens transformed?

Answer 29

both complexes are transported to cell membrane

Question 30

Where can MHC class I expression be found? What does it's role have to do with this?

Answer 30

- presents endogenous peptides from intercellular locations both self and non self - this is a form of ongoing surveillance of cell = expression through the body

Question 31

Where can MHC class II expression be found? What does it's role have to do with this?

Answer 31

- presents exogenous peptides from extracellular spaces and are specialized in leukocytes (WBC) - expression is restricted to antigen-presenting cells (dendritic cells, macrophages, and B cells)

Question 32

Which cells express MHC I?

Answer 32

all nucleated cells

Question 33

Why are self-peptides also presented to MHC cells and not just foreign antigens?

Answer 33

demonstrates the cell is healthy

Question 34

can a cell have many endogenous peptides presented at once?

Answer 34

yes - many MHC class I presented on antigen presenting cells

Question 35

What is the full process of a systolic pathogen infecting a cell and the role of MHC class I?

Answer 35

1. infection of cell 2. viral protein synthesized in cytosol 3. peptide fragments of pathogenic proteins bound by MHC class I in ER 4. bound peptides transported by MHC class I to cell surface

Question 36

What is a possible infection from intracellular pathogens?

Answer 36

infect cytosol and produce "endogenous" antigens

Question 37

What is significant about antigen presenting cells and MHC?

Answer 37

Since they are also nucleated cells, APCs can present antigens that come from: Endogenous (MHCI) AND Exogenous (MHCII)

Question 38

What is the summary of T cell differentiation?

Answer 38

1. Naive T-cells enter circulation and travel to SLT to encounter their antigens 2. T cell differentiation happens in SLT to give rise to effector T cells 3. Effector T-cells leave the SLT and enter the infected tissue (innate signaling) to either kill (CTL) or “help” (Th) control the infection