Immunology Lecture 10.

Question 1

What is the life cycle of a B cell?

Answer 1

1. generation of diverse and clonal expressed B-cell receptors in bone marrow 2. alteration, elimation, or inactivation of B cell receptors that bind to self (negative selection) 3. promotion of a fraction of immature B cells to become mature B cells in secondary lymphoid tissues (positive selection - not important like with T cells) 4. recirculation of mature B cells between lymph, blood, and secondary lymphoid tissues 5. activation and clonal expansion 6. differentiation to antibody-secreting plasma cells

Question 2

Where do B cells develop?

Answer 2

bone marrow

Question 3

What stage do B cells exit the bone marrow?

Answer 3

mature naive B cells (have not yet seen antigen)

Question 4

What do B and T cells develop from?

Answer 4

pluripotent progenitor cells

Question 5

CD34

Answer 5

marker for pluripotent hematopoietic stem cell

Question 6

What is the immunoglobulin status of an immature B cell?

Answer 6

a heavy and light chain. IgM on surface

Question 7

What does a pre-BCR do?

Answer 7

signals that a functional receptor has been made (from heavy chain - no light chain made yet)

Question 8

What is the importance of allelic exclusion with B cells?

Answer 8

gives homogeneous B-cell receptors with high-avidity binding

Question 9

What are most B cell light chains?

Answer 9

kappa (as opposed to lambda) because kappa chain always made first

Question 10

What are the two checkpoints in B cell development?

Answer 10

pre-B cell receptor - (selects for functional heavy chains) AND B-cell receptor (selects for functional light chains)

Question 11

TdT

Answer 11

adds diversity in junctional regions (N nucleotide addition)

Question 12

Burkitt’s Lymphoma

Answer 12

caused by a chromosomal aberration during B cell development - oncogenic effect

Question 13

What is the difference between a B1 cell and a B2 cell?

Answer 13

B1 produced by a fetus, more primitive, less developmental steps (more IgM) - self renewing, no need for T cell help

Question 14

What happens when a B cell reacts with self antigen?

Answer 14

immature B cell is retained in bone marrow where it goes through receptor editing (or dies)

Question 15

What happens when B cells binds to self antigen in periphery?

Answer 15

signaled to make IgD and become unresponsive to antigen, does not survive for long

Question 16

Where do B cells make final maturation?

Answer 16

periphery

Question 17

What is the main purpose of lymph nodes?

Answer 17

bring immune cells together

Question 18

What is a germinal center?

Answer 18

where maturation of B cells into high affinity happens (also plasma cells and memory cells) - intense competition for limiting antigen (somatic hypermutation)

Question 19

What stage in development does Hodgkin’s lymphoma arrise from?

Answer 19

germinal center B cell

Question 20

What stage in development does multiple myeloma arrise from?

Answer 20

plasma cell (hybridoma - monoclonal antibody)

Question 21

What is the order of development with B cells?

Answer 21

stem cell —> pro-B cell —> pre-B cell —> immature B cell —> mature naive B cell—> antigen activated lymphoblast (isotype switching) —> antibody-secreting plasma cell —> memory cell

Question 22

What happens to a B cell in the periphery?

Answer 22

naive lymphocytes arrive at lymph nodes in arterial blood, lymphocytes and lymph return to blood via lymphatics, venous blood returns to heart (pathogens from site of infection reach lymph nodes via lymphatics) - die if they don’t encounter antigen

Question 23

What defines B cells?

Answer 23

CD19

Question 24

How do B cells signal?

Answer 24

cross-linking of B cell receptors by antigen, phosphorylation, signaling cascade begins that creates activating signals

Question 25

Under what circumstance is T cell help not needed in B cell activation?

Answer 25

extensive cross-linking

Question 26

CD40

Answer 26

on B cell - CD40L on T cell activates, also causes release of IL-4,5,6 which cause B cell proliferation, resting memory cells, and plasma cells

Question 27

IL-4

Answer 27

induces IgG and IgE

Question 28

IL-5

Answer 28

augments production of IgA

Question 29

What happens in medullary cords of lymph nodes?

Answer 29

IgM response

Question 30

What is the main property of plasma cells?

Answer 30

just Ig secretion - don’t switch, don’t grow - factories

Question 31

Isotype of antibody produced by memory B cell?

Answer 31

IgG, IgA (higher affinity and somatic hypermutation)