8 B Cell Mediated Immunity I

Question 1

What is the signal transduction unit of the B cell receptor (BCR)?

Answer 1

IgAlpha and IgBeta complex crosslinking

Question 2

What is the co-recptor for the BCR?

Answer 2

Complement Receptor 2 (CR2) binding to C3b

Question 3

What signals are required for B cell activation?

Answer 3

BCR
CR2
T cell help

Question 4

What is the difference between Thymus Dependent and Thymus Independent Antigens?

Answer 4

Dependent Antigens need Costimulation by Helper T cell to activate B cells

Question 5

Do B cells and T cells that are in the Germinal center reaction have to have the same antigen to activate them?

Answer 5

No, they can be activated by different antigens

Question 6

What two ways do TI antigens overcome the need for T cell help?

Answer 6

1. TI-1 Antigens:
    Stimulate via different route: 
     Engage BCRs as well as PRRs
          these are known as "mitogens"
2. TI-2 Antigens:
       Heavily crosslink BCRs
           these usually respond to cell wall parts

Question 7

What do B1 cells respond to?

Answer 7

Cell wall polysaccarides

Question 8

What do mitogens activate?

Answer 8

Both BCRs and PRRs to activate B cells without T cell costimulation

Question 9

What are Infants and Toddlers unable to make that limit their response to cell wall antigens?

Answer 9

B1 B cells

Question 10

What type of activation of B cells do high concentration of TI-1 antigens illicit?

Answer 10

Polyclonal (not monoclonal) expansion and non-specific antibody response

Question 11

What type of activation of B cells do low concentrtion of TI-1 antigens illicit?

Answer 11

Antigen specific response, usually via IgM production

Question 12

What are the limitations of Thymus Independent (TI) responses?

Answer 12

Nonspecific 
No class switching
No Memory (so each response will have to start over)
B cell response never changes

Question 13

What type of antigen can infants and toddlers not respond to?

Answer 13

TI-2 antigens

usually cell wall components, crosslink BCRs

Question 14

Where do germinal center reactions occur?

Answer 14

Lymphoid follicles of secondary lymph (nodes)

Question 15

What happens in the germinal center?

Answer 15

somatic hypermutation
class switching
cytokine production

Question 16

What is an overview of B cell activation in the germinal center reaction?

Answer 16

1. Antigen-specific B cells enter the T cell zones
2. B cells interact with antigen-activated Th2 cells to form a primary locus
3. Germinal center reaction (positive selection and monoclonal expansion)
4. Plasma (early) and Memory (late) Cell production

Question 17

What are Follicular Dendritic Cells?

Answer 17

Use complement and antibodies to pick up antigens to present
Do not use MHC class II
Antigens 
Not APCs
Like a buffet of antigens

Question 18

What does IL 5 induce in class switching in B cells?

Answer 18

IgA class switching

Question 19

What does IL 4 induce in class switching in B cells?

Answer 19

IgE class switching

Question 20

What is virtually the only thing a Plasma Cell is used for?

Answer 20

Antibody production 30-60 days post infection

Question 21

What antibodies are found in the blood?

Answer 21

IgG
IgM
IgA

Question 22

What antibodies are found in the mucus?

Answer 22

IgA

Question 23

Where is IgE found?

Answer 23

Mast cell FceRI receptor in skin, BALT, GALT

Question 24

How do multimeric Igs enter the tissues from blood?

Answer 24

Poly-Ig receptor and transcytosis

Question 25

How do IgGs enter the tissues from blood?

Answer 25

Brambell receptor and transcytosis

Question 26

How do IgGs enter the placenta?

Answer 26

Brambell receptor (FcRn)

Question 27

What Ig is associated with crossing the placenta?

Answer 27

IgG

Question 28

What are examples of passive transfer of immunity?

Answer 28

Injection of antibodies

Maternal Ig’s via breast milk and placental barrier on Brambell receptors

Question 29

What fetal Ig is at the same concentration as maternal?

Answer 29

IgG

Question 30

What Ig is secreted in breast milk?

Answer 30

IgA

Question 31

How does the Ig of breast milk enter the tissues?

Answer 31

Poly-Ig Receptor

Question 32

When does infant IgM kick in?

Answer 32

5-9 months

Question 33

When do IgG and IgA kick in?

Answer 33

1 year to high levels

Question 34

What Fc Receptors were highlighted in lecture?

Answer 34

FcEpsilon Receptor: Binds IgE in mast cells
FcyReceptor III: Bind IgG1
Induce NK cells and APCs

Question 35

What do Ig’s need to be active? Exception?

Answer 35

Antibody needs to be bound

FcEpsilon is the exception (binds IgE free in blood to highjack for Mast cell use as antigen receptors)

Question 36

What WBC targets parasites coated with IgE?

Answer 36

Eosinophils