6- Development of B cells

Question 1

Where do B cells develop?

Answer 1

Bone marrow

Question 2

What do the B cells acquire during the first stage of B cell development?

Answer 2

Functional Ag receptors

Question 3

Why is the second stage of B cell develolpment called “negative selection?”

Answer 3

Because it gets rid of B cells that react to the bodys own tissues

Question 4

What occurs during the 3rd (positive selection) stage of B cell development?

Answer 4

Immature B cells compete for the limited # of sites in the follicles of the secondary lymphatic tissues.

Question 5

Where do the B cells go in the fourth stage of B cell development?

Answer 5

The mature B cells travel in the blood and lymph looking for infection.

Question 6

What occurs when an Ag binds to the BCR during the 5th stage of B cell development?

Answer 6

It leads to proliferation and clonal expansion of The Ag-specific B cell.

Question 7

What do B cells morph into during the 6th stage of B cell development?

Answer 7

Plasma cells

Question 8

What is the fxn of plasma cells?

Answer 8

They provide Ab’s that attack ongoing infection and create memory B cells for the quick killing of future infections.

Question 9

What occurs when the B cell is a “pro B cell?”

Answer 9

Rearrangement of the heavy genes

Question 10

What type of markers are identifiable in pro-B cells?

Answer 10

TdT, MHC-II, CD19, CD20, CD, 21, and CD40.

Question 11

What is the first type of heavy chain produced in the “pre-B cell?”

Answer 11

μ heavy chain

Question 12

What occurs when the B cell is a pre-B cell?

Answer 12

Rearrangement of the light chains.

Question 13

What is expressed on the cell surface of immature B cells?

Answer 13

IgM (μ chains + light chains) + Igα & Igβ polypeptides

Question 14

Which Ab is expressed on the cell surface on mature B cells?

Answer 14

IgD

Question 15

Clinical Q: An analysis of B cells during development reveal cytoplasmic μ+. Which stage of B cell development are the B cells in?

Answer 15

Pre-B cells

Question 16

Clinical Q: An analysis of B cells during development reveal surface IgD. Which stage of B cell development are the B cells in?

Answer 16

Mature B cell

Question 17

Clinical Q: An analysis of B cells during development reveal no surface or cytoplasmic markers other than the normal CD20, TdT and MHC-II. Which stage of B cell development are the B cells in?

Answer 17

Pro-B cell

Question 18

Clinical Q: An analysis of B cells during development reveal surface IgM and it’s the only Ab on the surface. Which stage of B cell development are the B cells in?

Answer 18

Immature B cell

Question 19

Which Ab’s do memory cells have on their surface?

Answer 19

IgG, IgA, or IgE

Question 20

What is the fxn of stromal cells in B cell development?

Answer 20

They both make specific contacts with developing B cells and produce growth factors for the B cell.

Question 21

What is the function of the surrogate light chain?

Answer 21

It mimics an Ig light chain and forms the pre-BCR

Question 22

What happens if the μ chain assembles poorly with the surrogate light chain?

Answer 22

A functional BCR isn’t make and the cell dies by apoptosis

Question 23

What is the fxn of Btk (brutons tyrosine kinase)?

Answer 23

It’s involved with signal transduction and B cell development beyond the pre-B cell stage.

Question 24

What are λ5 & VpreB’s?

Answer 24

They are pre-BCR’s

Question 25

What are the functions of Igα & Igβ?

Answer 25

They form pre-BCR's and BCR's

Question 26

When are Igα &Igβ turned off?

Answer 26

When Ag-stimulated B cells differentiate into plasma cells.

Question 27

What is missing in an agammaglobulinemia patient?

Answer 27

Btk gene

Question 28

What is the clinical basis for agammaglobulinemia symptoms?

Answer 28

No Btk --> no circulating Ab's --> recurrent infections

Question 29

What is the main fxn of CD5 B-1 cells?

Answer 29

They are weird B cells that make Ab's against common bacterial polysaccharides.

Question 30

What type of disease is caused from B-1 cells that develop postnatally?

Answer 30

Chronic lymphocytic leukemia (CLL)

Question 31

What stage of B cell development does B cell selection occur?

Answer 31

Immature B cells

Question 32

What is the purpose of B cell selection?

Answer 32

Get rid of B cells that react to self-Ag's and keep those which express IgM and IgD for pathogenic Ag's

Question 33

What happens to an immature B cell if it binds to self-Ag's?

Answer 33

it's signaled to continue light chain gene rearrangement or to die by apoptosis.

Question 34

Which chemokine attracts immature B cells in the blood to the HEV?

Answer 34

CCL21

Question 35

Which chemokines attract the B cells into the lymph node?

Answer 35

CCL21 and CCL19

Question 36

Which chemokine, secreted from folicular dendritic cells, attracts B cells into the primary follicle?

Answer 36

CXCL13

Question 37

What happens when immature B cells enter the follicle?

Answer 37

They interact with protein on FDC's that signal their final maturation into a mature B cell. yay.

Question 38

Where in the lymph nodes do B cells mature to plasma cells?

Answer 38

Germinal centers

Question 39

What causes a B cell to differentiate into a plasma cell?

Answer 39

Activation by CD4 T cells.

Question 40

What type of Ab's do plasma cells secrete?

Answer 40

IgM

Question 41

What is the job of the plasma cell?

Answer 41

They're a memory cell that continuously synthesizes and secretes an Ab for an Ag that the body once encountered.

Question 42

Which stages of B cell development are "antigen independent?"

Answer 42

Stem cell --> pro-B --> pre-B --> Immature B --> mature B

Question 43

What are the "antigen dependent" stages of B cell development?

Answer 43

Mature B cell --> plasma cell or memory cell

Question 44

What are naive B cells?

Answer 44

They're mature B cells that left the bone marrow but have not yet encountered its specific Ag

Question 45

What are memory cells?

Answer 45

They're Ag-specific B cells that are produced from activated B cells during a primary infection

Question 46

What causes memory cells to differentiate into plasma cells?

Answer 46

Subsequent exposure to their specific Ag