Immune System - Lecture 4 Part A

Question 1

Where are B cells produced?

Answer 1

In the bone marrow

Question 2

What are B cells responsible for?

Answer 2

The humoral immune defense or the antibody mediated immune response

Question 3

What do B cells differentiate into?

Answer 3

Effector plasma cells

Question 4

What are Effector Plasma Cells?

Answer 4

Differentiated B cells that are antibody producers

Question 5

What receptor do B cells have on them?

Answer 5

B cell receptor (BCR)

Question 6

What is different about the B cell receptors (BCR)?

Answer 6

The BCR is actually an antibody that is bound to its membrane

Question 7

What is the Coreceptor that B cells have?

Answer 7

CD21

Question 8

What does CD21 of B cells do?

Answer 8

Binds to complement proteins C3B

Question 9

What does the binding of the CD21 coreceptor of B cells to C3B do?

Answer 9

Opsonizes the antigen increasing the strength of the binding between the B cells and the antigen

Question 10

With B cells what is an antigen bound to?

Answer 10

The antigen is simultaneous bound to the B cell receptor (BCR) and indirectly by CD21

Question 11

What happens once the B cell is activated?

Answer 11

Signal transduction happens, leading to antibody productions

Question 12

What do B Cell Receptors (BCRs) consist of?

Answer 12

Four polypeptide chains
•Two identical light chains
•Two identical heavy chains

Question 13

What do both the light and heavy chains of BCRs have?

Answer 13

Variable and constant amino acid sequences

Question 14

Which region of BCRs are where the antigen binds?

Answer 14

The variable regions

Question 15

What makes B cells antigen specific cells?

Answer 15

Their variability based on which antigen it binds

Question 16

How long does maturation of B cells take?

Answer 16

One to two weeks

Question 17

What do stromal cells found in the bone marrow do?

Answer 17

Support B cell development by producing cytokines and chemokines

Question 18

What do Hematopoietic cells turn into in regards to B cells?

Answer 18

Pro-B cells

Question 19

What do Pro-B cells turn into?

Answer 19

Pre-B cells

Question 20

What happens during the Pre-B cell development stage?

Answer 20

Cells that express the BCR survive and cells that do not express the receptor die by apoptosis

Question 21

What do the surviving cells of the Pre-B stage do?

Answer 21

Generate a pool of daughter cells with the same heavy chain but a light chain that undergoes DNA arrangement

Question 22

What accounts for the variability of the antigen binding site in B cells?

Answer 22

The DNA arrangement that the light chain undergoes in the pre-B stage

Question 23

What happens once the DNA arrangement of the light chain on Pre-B cells is complete?

Answer 23

The IgM receptor is expressed on B cells and the cell becomes an immature B cell

Question 24

When does a cell become an immature B cell?

Answer 24

When the IgM receptor is expressed on them

Question 25

What happens once immature B cells express IgM?

Answer 25

The immature B cells leave the bone marrow and migrate towards the spleen where they go to complete their maturation

Question 26

Where do immature B cells complete their maturation?

Answer 26

In the spleen

Question 27

What do immature B cells develop in the spleen to make them mature?

Answer 27

The IgD receptor

Question 28

What does the ability of B cells to respond to antigens depend on?

Answer 28

IgM and IgD

Question 29

What is a mature B cell positive in?

Answer 29

IgM and IgD

Question 30

Why is B cell development simpler than T cell development?

Answer 30

Because B cells can recognize unprocessed antigens so they don't need to be on an antigen presenting cell or MHC molecule

Question 31

What must mature B cells be tested for?

Answer 31

Their affinity for self antigens

Question 32

Why do B cells need to be checked for their affinity for self antigens?

Answer 32

To prevent autoreactive antibodies from being produced

Question 33

In which part of the body does the checking for autoreactive B cells occur?

Answer 33

In the bone marrow

Question 34

What would occur if a B cell has a strong affinity for self antigens?

Answer 34

The B cell will undergo receptor editing

Question 35

What is receptor editing?

Answer 35

Changing the light chain of the BCR to change the specificity of the antigen so that it won't be autoreactive

Question 36

What happens if receptor editing of a B cell fails?

Answer 36

The cell will receive death signals and die by apoptosis

Question 37

What happens if the B cell recognizes self antigens with low avidity?

Answer 37

The B cell will survive but the antigen receptor expression is reduced and the cell will become anergic

Question 38

What type of antigens are B lymphocytes activated by?

Answer 38

A wide variety of antigens, including polysaccharides, lipids, nucleic acids and even small chemicals

Question 39

What are the two ways that B lymphocytes can be activated?

Answer 39

* T cell dependent activation | * T cell independent activation

Question 40

How does T cell dependant activation of B cells work?

Answer 40

A naïve CD4+ T cell or T helper cell being activated by an antigen presenting cell differentiates into an effector cell. The naïve B cell binds to the same antigen on the T helper cell and begins displaying the same antigen through MHC II and the engagement of T and B cells stimulates the proliferation and differentiation into plasma cell which will secrete IgM antibodies

Question 41

What happens after activated B cells differentiate into plasma cells and secrete IgM antibodies?

Answer 41

Some cells will migrate back to germinal centers and proliferate a more specialized body's response. This is when genetic rearrangement occurs

Question 42

What is class switching in B cell activation?

Answer 42

When other class of B cell antibodies are produced for more high affinity antibodies

Question 43

What is the outcome of the T cell dependent B cell activation?

Answer 43

A highly specialized process with the production of high affinity antibodies to eliminate pathogens

Question 44

What is Class Switching in T Cell Dependant - B cell activation induced by?

Answer 44

T helper cells

Question 45

What is Class Switching?

Answer 45

The process of changing the isotype of the antibody produced

Question 46

What does the process of isotype switching do?

Answer 46

Increases functional capabilities of the humoral immune response

Question 47

What is changed is Isotype switching?

Answer 47

The heavy chain

Question 48

What is T cell independent B cell activation usually triggered by?

Answer 48

Polysaccharides and lipids and other non protein antigens

Question 49

What is one type of T cell independent B cell activation using C3B?

Answer 49

When the complement system is activated by a pathogen the pathogen becomes coated with C3B which is recognized by the B cell coreceptors

Question 50

How does T cell independent B cell activation occur using PRRs?

Answer 50

Toll-like receptor membranes recognize PAMPs which leads to B cell activation. However a lot of antigens is required for this and low affinity antibodies are produced

Question 51

What do Memory B cells do?

Answer 51

Circulate in the cells and don't react unless the antigen

Question 51

What do Memory B cells do?

Answer 51

Circulate in the cells and don't react unless the antigen is reintroduced