Immunology 6

Question 1

what is the function of a B cell?

Answer 1

to give rise to plasma cells that secrete antibodies capable of binding to an organism, microbe, or molecule

Question 2

the secreted antibodies have antigen binding sites…

Answer 2

identical to those of the receptor molecules on the B-cell surface

Question 3

antibodies belong to the class of proteins known as ?

Answer 3

immunoglobulins

Question 4

B cells develop first from hematopoietic stem cells, and then into common lymphoid progenitors under the influence of ?

Answer 4

IL-7

Question 5

B cells are released into circulation as ?

Answer 5

immature, naive B cells

Question 6

B cells develop from common lymphoid precursors into

Answer 6

Pre-pro B cells

Question 7

As the pro-B cell matures to a pre-B cell, it will express an ?

Answer 7

immature BCR (B-cell receptor)

Question 8

If this BCR is ? the B cell passes the pre-B cell checkpoint and becomes a pre-B cell

Answer 8

productive

Question 9

If this BCR is ? the B cells will undergo apoptosis

Answer 9

unproductive

Question 10

Prior to maturation into an immature B cells, the Pre-B cell goes through a second checkpoint.
At this point the BCR is checked for ?

Answer 10

self-reactivity

Question 11

Explain if Pre-B cells is positive for self-reactivity

Answer 11

○ If (+): Pre-B cells tries to rearrange light chain genes of the BCR and will be checked again for self-reactivity
§ If still (+) -> Pre-B cell will undergo apoptosis

Question 12

Explain if Pre-B cells is negative for self-reactivity

Answer 12

If (-) -> becomes a immature (aka transitional) B cell and leaves the bone marrow

Question 13

From the bone marrow immature (aka transitional) B cells travel to the ?

Answer 13

spleen

Question 14

once in the spleen, the immature B cell begins expressing:

Answer 14

• CD21 - the complement co-receptor
• IgD in addition to IgM as the isomer of the portion of the BCR

Question 15

From general circulation, the B cell will migrate to ?

Answer 15

a lymphoid follicle within a lymph node

Question 16

what are bean-shape structures encapsulated with a reticular network and packed full of lymphocytes, macrophages, and dendritic cells

Answer 16

lymph nodes

Question 17

what are the 3 main regions of lymph nodes

Answer 17

• cortex
• paracortex
• medulla

Question 18

what is in the cortex region?

Answer 18

Contains lymphocytes (predominantly B-cells), macrophages and follicular dendritic cells arranged into primary follicles

Question 19

what is in the paracortex region?

Answer 19

contains mostly T-lymphocytes and dendritic cells

Question 20

what is in the medulla?

Answer 20

• More sparsely populated with lymphoid-lineage cells
  ○ Often plasma cells actively secreting antibody molecules

Question 21

Within a lymph node, a naïve B-cell encounters an antigen in 1 of 2 ways:

Answer 21

1. The antigen flows into a lymph node through afferent lymphatics and binds to the BCR
2. Macrophages or dendritic cells encounter an antigen in the periphery and bring it to a lymph node
   
   • Here they will “present” the antigen to a B cell and the antigen binds to the BCR

Question 22

The antigen binds to the BCR with the help of:

Answer 22

B-cell co-receptor:
- CD21: co-receptor that binds an antigen bound to the complement component C3d
- CD19: signal transduction protein

Question 23

Once the B-cell has presented it’s antigen it will also increase its expression of co-stimulatory molecules:

Answer 23

• CD80/86
• ICOSL
• CD40

Question 24

CD80/86 on B-cell binds to CD28 on T-helper cells for ?

Answer 24

T-cell activation

Question 25

ICOSL on B-cell Binds to iCOS on T-helper cells to induce

Answer 25

Cytokine productions

Question 26

CD40 on B-cells binds to CD40L on T-helper cells to ?

Answer 26

increase antibody production

Question 27

Then the B-cell will present it's antigen to which type of T-helper cell?

Answer 27

Tfh

Question 28

Under the influence of ?, the B cell will proliferate and begin to produce antibodies

Answer 28

IL-2, IL-4 (by Tfh cell), and CD40-CD40L interaction

Question 29

What will result in production of high-affinity antibodies?

Answer 29

somatic hypermutation

Question 30

During antibody class switching, ? may be switched to a different class

Answer 30

the original antibody (IgM)

Question 31

what secreted by the T-helper cells will induce class switching

Answer 31

different cytokines

Question 32

T-helper 1 cells secrete INF-y which stimulates class switching to ?

Answer 32

IgG subtypes

Question 33

TGF-beta stimulates class switching to ?

Answer 33

IgA

Question 34

T-helper 2 cells secrete IL-4 and IL-5, which stimulates class switching to ?

Answer 34

IgE

Question 35

what are the steps of somatic hypermutation?

Answer 35

1. The B cell starts in the dark zone of the germinal center where it will loses its HLA expression and mutate it's BCR genes 2. The BCR moves into light zone of the germinal center and samples follicular dendritic cells for the antigen

Question 36

Following B-cell selection in germinal center for high-affinity antibodies, the B cell differentiates into either:

Answer 36

- plasma cells - memory B cells

Question 37

what do plasma cells do?

Answer 37

No longer have BCR and secrete a large number of antibody molecules

Question 38

what do memory B cells do?

Answer 38

Circulate in the periphery: Once they re-encounter their specific antigen, they will proliferate and differentiate into plasma cells

Question 39

what is the structure of an antibody?

Answer 39

2 heavy chains and 2 light chains, and has constant and variable regions

Question 40

what regions undergoes genetic shuffling for antibodies

Answer 40

variant regions

Question 41

what are the 6 categories of antibody functions?

Answer 41

1. Neutralization 2. Agglutination 3. Opsonization 4. Complement activation 5. anti-body dependent cell mediated cytotoxicity 6. degranulation

Question 42

what are the 5 main classes of antibodies?

Answer 42

- IgM - IgG - IgD - IgE - IgA

Question 43

what is the first class of antibody secreted during the primary immune response

Answer 43

IgM

Question 44

what is IgM secreted as ?

Answer 44

a pentamer

Question 45

IgM tends to have a higher or lower affinity for its antigen?

Answer 45

lower

Question 46

what are the functions of IgM?

Answer 46

- Very good at activating complement - Good at agglutinating pathogens - immobilizes the pathogens allowing for phagocytosis

Question 47

what is the most common antibody found in serum?

Answer 47

IgG

Question 48

IgG is secreted as a ?

Answer 48

monomer

Question 49

what are the variety of different classes of IgG?

Answer 49

IgG1, IgG2, IgG3, IgG4

Question 50

what are the functions of IgG?

Answer 50

- Opsonization § Bind the Fc receptor on phagocytes and enhances phagocytosis - IgG1 and IgG3 are good at activating complement - IgG2alpha is good at triggering antibody-mediated cytotoxicity by Natural killer cells

Question 51

what is predominantly found as a dimer secreted into tears, saliva, breastmilk, and mucus?

Answer 51

IgA

Question 52

what are the functions of IgA?

Answer 52

- Neutralizing pathogens - Agglutinating pathogens

Question 53

IgE is secreted as ?

Answer 53

a monomer in small quantities

Question 54

what is the function of IgE

Answer 54

Binds to cells with and Fc receptor for IgE triggering degranulation of granulocyte

Question 55

IgD is secreted as ?

Answer 55

a monomer in very small quantities

Question 56

IgD is most prevalent in secretions of the ?

Answer 56

upper respiratory tract

Question 57

IgD binds to ?

Answer 57

basophils and mast cells