10.9 T and B cells

Question 1

_ cells are responsible for neutralization of microbes, phagocytosis, and complement activation

Answer 1

B cells are responsible for neutralization of microbes, phagocytosis, and complement activation

Question 2

_ cells are needed for effective innate and adaptive immunity; they activate macrophages, increase inflammation, and cause proliferation/differentiation of T and B lymphocytes

Answer 2

Helper T cells are needed for effective innate and adaptive immunity; they activate macrophages, increase inflammation, and cause proliferation/differentiation of T and B lymphocytes

Question 3

CD8+ cells directly kill infected cells by release of _ and _

Answer 3

CD8+ cells directly kill infected cells by release of perforin and granzyme

Question 4

_ cells (of adaptive immunity) help to suppress the immune response

Answer 4

Treg cells (of adaptive immunity) help to suppress the immune response

Question 5

B cells can float around and find antigen; however, T cells must be presented with antigen on _

Answer 5

B cells can float around and find antigen; however, T cells must be presented with antigen on MHC (in the form of small peptides)
* Antibodies can be secreted and travel in bloodstream
* T cells must always have constant region in the membrane

Question 6

The TCR is made up of two arms, the _ and _

Answer 6

The TCR is made up of two arms, the alpha and beta

Question 7

(True/ False) VDJ recombination occurs in the TCR

Answer 7

True; VDJ recombination occurs in the TCR
* Occurs in the thymus

Question 8

HLA-A, HLA-B, and HLA-C are all (MHC I/ MHC II)

Answer 8

HLA-A, HLA-B, and HLA-C are all MHC I

Question 9

HLA- DP, HLA- DQ, HLA-DR are all (MHC I/ MHC II)

Answer 9

HLA- DP, HLA- DQ, HLA-DR are all MHC II

Question 10

MHC I can be found _

Answer 10

MHC I can be found on all nucleated cells
* RBCs do not have MHC I

Question 11

MHC II can be found _

Answer 11

MHC II can be found only on professional APCs

Question 12

Why is it significant that all cells in the body have MHC I?

Answer 12

All cells have MHC I so that we can constantly surveil our cells and kill off malignant/ infected cells if needed (CD8+)

Question 13

MHC I presents (endogenous/ exogenous) peptides

Answer 13

MHC I presents endogenous peptides

Question 14

MHC II presents (endogenous/ exogenous) peptides

Answer 14

MHC II presents exogenous peptides

Question 15

(MHC I/ MHC II) contains two chains (alpha and beta) of equal length

Answer 15

MHC II contains two chains (alpha and beta) of equal length
* Both chains are transmembrane
* Both alpha and beta bind peptide

Question 16

(MHC I/ MHC II) contains beta2-microglobulin for stability

Answer 16

MHC I contains beta2-microglobulin for stability

Question 17

In MHC I, only _ chain forms the peptide binding cleft

Answer 17

In MHC I, only alpha chain forms the peptide binding cleft

Question 18

TAP and proteasome are part of (MHC I/ MHC II) processing and presentation

Answer 18

TAP and proteasome are part of MHC I processing and presentation

Question 19

The invariant chain is a part of (MHC I/ MHC II) processing and presentation

Answer 19

The invariant chain is a part of MHC II processing and presentation

Question 20

Steps of MHC I processing and presentation

Answer 20

MHC I:
1. Endogenous, cytosolic protein
2. Antigen is processed in the proteasome which chops it into small peptides
3. Antigen then travels to the transporter associated antigen processing protein (TAP) which gives the antigen access into the ER
4. In the ER, the antigen binds MHC
5. Travels to get expressed on the outside of the cell

Question 21

Steps of the MHC II processing and presentation

Answer 21

MHC II:
1. Exogenous antigen undergoes endocytosis
2. Invariant chain is involved in MHC biosynthesis
3. MHC and peptide find each other in endocytic vesicle (not in ER)
4. Travels to get expressed on the outside of the cell

Question 22

CD4+ cells have multiple effector functions:

Answer 22

CD4+:
* Activate macrophages for destruction of phagocytosed antigen
* B cell antibody secretion: antibody binding to antigen
* We need CD4+ to stimulate class switch from IgM to make effective antibodies

Question 23

T cells originate in the _ but
mature in the _

Answer 23

T cells originate in the bone marrow but
mature in the thymus

Question 24

VDJ recombination for T cells happens in the _

Answer 24

VDJ recombination for T cells happens in the thymus

Question 25

Where would we find a CD4+CD8+ cell?

Answer 25

**Double positive** T cells are still in the maturation process so they could be found in the **thymus**

Question 26

MHC II pathway involves loading peptides from the endosome/lysosome (internalized); we rely on _ enzymes to generate peptides

Answer 26

MHC II pathway involves loading peptides from the endosome/lysosome (internalized); we rely on **endosomal and lysosomal proteases** to generate peptides * Versus MHC I pathway which uses a proteasome

Question 27

The peptide loading site onto MHC I is the _

Answer 27

The peptide loading site onto MHC I is the **Endoplasmic reticulum**

Question 28

The peptide loading site of MHC II is the _

Answer 28

The peptide loading site of MHC II is the **specialized vesicular compartment**

Question 29

Naive T cells will recycle from lymph nodes to the blood seeking encounters from pathogens; if pathogen is not presented, naive T cells die within _

Answer 29

Naive T cells will recycle from *lymph nodes to the blood* seeking encounters from pathogens; if pathogen is not presented, naive T cells die within **5-7 weeks**

Question 30

The main secondary signal required to activate T cell is _ and _ binding

Answer 30

The main secondary signal is **CD28-B7** * A second co-stimulatory signal is required to induce complete T cell activation * CD28 is on the T cell * B7 is on the APC

Question 31

The three most common subtypes of T helper cells are _ , _ , and _

Answer 31

The three most common subtypes of T helper cells are **Th1** , **Th2** , and **Th17** * *All of these have different functions and the dendritic cells will tell us what pathogen is out there and decide which T helper cell is needed*

Question 32

Th1 cells secrete _ cytokines

Answer 32

Th1 cells secrete **IFN gamma** * Th1 cells are the most commonly used

Question 33

_ T helper cell is primarily responsible for macrophage activation and IgG production

Answer 33

**Th1** is primarily responsible for macrophage activation and IgG production * Secreted against intracellular microbes * Associated with autoimmune diseases and tissue damage in chronic infections

Question 34

_ T helper cell is secreted against helminthic and parasitic infections; it leads to mast cell and eosinophil activation, IgE production

Answer 34

**Th2** is secreted against helminthic and parasitic infections; it leads to mast cell and eosinophil activation, IgE production

Question 35

_ T helper cell is secreted when we have a bacterial or fungal infection; it activates neutrophils and monocytic inflammation

Answer 35

**Th17** is secreted when we have a bacterial or fungal infection; it activates neutrophils and monocytic inflammation

Question 36

Th2 cells secrete _ cytokines

Answer 36

Th2 cells secrete **IL-4, IL-5, IL-13**

Question 37

Th17 cells secrete _ cytokines

Answer 37

Th17 cells secrete **IL-17, IL-22**

Question 38

CD8+ cells cause apoptosis of target cells by secreting _ and _

Answer 38

CD8+ cells cause apoptosis of target cells by secreting **perforin** and **granzymes**

Question 39

Natural killer cells destroy virally infected cells by binding to surface receptors for _

Answer 39

Natural killer cells destroy virally infected cells by binding to surface receptors for **IgG** * *IgG is an antibody that coats the antigen for destruction by NK cells*

Question 40

Natural killer cells secrete _ and _

Answer 40

Natural killer cells secrete **perforin** and **granzyme**

Question 41

T lymphocytes undergo central tolerance in the thymus where they have 2 possible routes:

Answer 41

Central tolerance in the thymus: 1. **Deleted** via negative selection 2. Become **Treg** cells

Question 42

B lymphocytes undergo central tolerance in the bone marrow where they have 3 possible routes:

Answer 42

B lymphocytes undergo central tolerance in the bone marrow where they have 3 possible routes: 1. **Deletion** via negative selection 2. **Anergy** (bind but inactive) 3. **Receptor editing** (second chance)

Question 43

(T lymphocytes/ B lymphocytes) can get a second chance during central tolerance; they undergo receptor editing

Answer 43

**B lymphocytes** can get a second chance during central tolerance; they undergo receptor editing

Question 44

Peripheral tolerance happens in _ and _

Answer 44

Peripheral tolerance happens in **spleen** and **lymph nodes**

Question 45

Regulatory T cells will go to _ and inhibit responses against self-antigens by secreting _ and _

Answer 45

Regulatory T cells will go to **periphery** and inhibit responses against self-antigens by secreting **IL-10** and **TGF-beta** * They have special transcription factors and markers associated with them (CD3+CD4+CD25 and FoxP3+) * Their development is independent of AIRE

Question 46

In addition to inhibitory cytokines, Treg cells also suppress immune response via expression of _ and _

Answer 46

In addition to inhibitory cytokines, Treg cells also suppress immune response via expression of **CTLA-4** and **IL-2 receptors to capture IL-2**