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Physl > Immune System - Lecture 4 Part A > Flashcards

Immune System - Lecture 4 Part A Flashcards

1
Q

Where are B cells produced?

A

In the bone marrow

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2
Q

What are B cells responsible for?

A

The humoral immune defense or the antibody mediated immune response

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3
Q

What do B cells differentiate into?

A

Effector plasma cells

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4
Q

What are Effector Plasma Cells?

A

Differentiated B cells that are antibody producers

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5
Q

What receptor do B cells have on them?

A

B cell receptor (BCR)

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6
Q

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

A

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

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7
Q

What is the Coreceptor that B cells have?

A

CD21

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8
Q

What does CD21 of B cells do?

A

Binds to complement proteins C3B

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9
Q

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

A

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

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10
Q

With B cells what is an antigen bound to?

A

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

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11
Q

What happens once the B cell is activated?

A

Signal transduction happens, leading to antibody productions

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12
Q

What do B Cell Receptors (BCRs) consist of?

A

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

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13
Q

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

A

Variable and constant amino acid sequences

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14
Q

Which region of BCRs are where the antigen binds?

A

The variable regions

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15
Q

What makes B cells antigen specific cells?

A

Their variability based on which antigen it binds

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16
Q

How long does maturation of B cells take?

A

One to two weeks

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17
Q

What do stromal cells found in the bone marrow do?

A

Support B cell development by producing cytokines and chemokines

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18
Q

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

A

Pro-B cells

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19
Q

What do Pro-B cells turn into?

A

Pre-B cells

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20
Q

What happens during the Pre-B cell development stage?

A

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

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21
Q

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

A

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

22
Q

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

A

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

23
Q

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

A

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

24
Q

When does a cell become an immature B cell?

A

When the IgM receptor is expressed on them

25
Q

What happens once immature B cells express IgM?

A

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

26
Q

Where do immature B cells complete their maturation?

A

In the spleen

27
Q

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

A

The IgD receptor

28
Q

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

A

IgM and IgD

29
Q

What is a mature B cell positive in?

A

IgM and IgD

30
Q

Why is B cell development simpler than T cell development?

A

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

31
Q

What must mature B cells be tested for?

A

Their affinity for self antigens

32
Q

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

A

To prevent autoreactive antibodies from being produced

33
Q

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

A

In the bone marrow

34
Q

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

A

The B cell will undergo receptor editing

35
Q

What is receptor editing?

A

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

36
Q

What happens if receptor editing of a B cell fails?

A

The cell will receive death signals and die by apoptosis

37
Q

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

A

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

38
Q

What type of antigens are B lymphocytes activated by?

A

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

39
Q

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

A
  • T cell dependent activation

* T cell independent activation

40
Q

How does T cell dependant activation of B cells work?

A

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

41
Q

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

A

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

42
Q

What is class switching in B cell activation?

A

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

43
Q

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

A

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

44
Q

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

A

T helper cells

45
Q

What is Class Switching?

A

The process of changing the isotype of the antibody produced

46
Q

What does the process of isotype switching do?

A

Increases functional capabilities of the humoral immune response

47
Q

What is changed is Isotype switching?

A

The heavy chain

48
Q

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

A

Polysaccharides and lipids and other non protein antigens

49
Q

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

A

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

50
Q

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

A

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

51
Q

What do Memory B cells do?

A

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

51
Q

What do Memory B cells do?

A

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

Physl (94 decks)

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