Exam II - B Cell Questions

Question 1

Where do B cells mature?

Answer 1

Bursa of Fabricious (birds) or Bone Marrow

Question 2

Which 2 Igs make up the BCRs?

Answer 2

IgM, IgD

Question 3

What is the function of a BCR?

Answer 3

To recognize and react to an antigen

Question 4

What is the life span of most B Cells?

Answer 4

Most are short lived. Memory B cells are long-lived

Question 5

What are the 2 ‘hallmark events’ of B cell development?

Answer 5

1. expression of antigen receptor genes by the immature B cell
2. functional competence

Question 6

Which cytokine stimulates B Cell proliferation?

Answer 6

IL-7

Question 7

Which BCR component is expressed on Pre-B cells?

Answer 7

IgM heavy chains

Question 8

Which BCR component is expressed on mature naive B cells?

Answer 8

IgD along with IgM

Question 9

At which step of maturation is functional competence achieved?

Answer 9

Full maturation; when B cell expresses both IgM and IgD

Question 10

Where are B cells found after maturation?

Answer 10

Peripheral lymphoid organs and tissues (lymph nodes, MALT, GALT, etc…)

Question 11

What is the fate of Ag bound to the BCR?

Answer 11

the antigen is endocytosed into a phagosome, merges with a lysosome to become a phagolysosome, which digests the antigen so that it can be presented by MHC class II molecules

Question 12

What is the signal transduction protein associated with the BCR?

Answer 12

CD79

Question 13

Which gene regions encode the lambda and kappa light chain proteins?

Answer 13

Chromosome 2 for kappa chain; Chromosome 22 for lambda chain

Question 14

What is the purpose of somatic gene rearrangement?

Answer 14

It results in Ig diversity, and ensures that only B cells will produce immunoglobulins

Question 15

Which light chain is rearranged 1st?

Answer 15

kappa

Question 16

Which enzymes are responsible for cleaving DNA at recombination requences?

Answer 16

Recombinases

Question 17

What cell types synthesize recombinase?

Answer 17

T and B lymphocytes

Question 18

Which enzymes are responsible for repairing the double strand breaks?

Answer 18

DNA repair enzymes

Question 19

DNA-dependent protein kinase is an example of a:

Answer 19

DNA repair enzyme

Question 20

Which species/breed is known to suffer from Severe Combined Immunodeficiency (SCID)?

Answer 20

Arabian foals

Question 21

Which lymphocytes will an animal with SCID be unable to synthesize?

Answer 21

T and B lymphocytes

Question 22

Which receptors constitute the B cell coreceptor complex?

Answer 22

CR2, CD19, CD81

Question 23

The CD21 receptor binds to:

Answer 23

C3d

Question 24

The binding of which receptor and ligand facilitates activation of a B cell?

Answer 24

CD40 to CD40L

Question 25

What can a T_H cell secrete to help activate a B cell?

Answer 25

IL-2, IL-4, IL-6

Question 26

What cell type do most B cells differentiate into?

Answer 26

Plasma cells

Question 27

"terminally differentiated B cells" are also called:

Answer 27

plasma cells

Question 28

Where are plasma cells found?

Answer 28

extrafollicular sites in peripheral lymphoid organs, and at a few inflammatory sites. Few are found in circulation

Question 29

What is a tumor of plasma cells called?

Answer 29

multiple myeloma.

Question 30

How do plasma cell tumors arise?

Answer 30

They are the result of a random mutation in a single B cell

Question 31

What kind of Ig does a plasma cell tumor produce?

Answer 31

They produce homogenous Ig called *Myeloma Protein (M Protein)*

Question 32

What is light chain disease?

Answer 32

Myeloma in which Ig light chains are produced alone or are predominant

Question 33

What are the consequences of light chain disease?

Answer 33

They pass through the glomerulus and are excreted in the urine. They are toxic to renal tubular cells and cause renal failure

Question 34

These are proteins that precipitate when heated to 60^oC

Answer 34

Bence Jones proteins

Question 35

What is the life span of Bence Jones proteins?

Answer 35

These cells survive indefinitely in cell culture

Question 36

Which proteins regulate somatic mutations?

Answer 36

Protein antigens

Question 37

What is the net result of affinity maturation?

Answer 37

A population of B cells that produce antibodies with significantly higher affinities for antigen

Question 38

What is required for the development of memory B cells?

Answer 38

T cell-derived cytokines

Question 39

Which cells to T-independent antigens bind?

Answer 39

B cells

Question 40

What is the 1^o antibody produced in response to T-independent Ags?

Answer 40

IgM

Question 41

What happens to lymphocutes bearing receptors specific for self-peptides?

Answer 41

They are deleted at an early stage of development

Question 42

Define mitogen

Answer 42

A mitogen is capable of inducing cell division in a high percentage of T or B cells

Question 43

List some examples of T and B cell mitogens

Answer 43

Pokeweed, LPS, Protein A, Phytohemagglutinin, Concanavalin A.

Question 44

How are the properties of mitogens used clinically?

Answer 44

To assess the ability of lymphocytes from patients with suspected immunodeficiency

Question 45

Which Ig shows N-region diversity?

Answer 45

**IgH** TdT is expressed by Pro-B cell only during the stage of IgH gene rearrangement. Therefore, only IgH shows N-region diversity.

Question 46

During which stages are the RAGs expressed?

Answer 46

Pro, Pre

Question 47

During which stage(s) is TdT expressed?

Answer 47

Just Pro-B

Question 48

What are the progeny of B cells?

Answer 48

plasma cells and memory cells

Question 49

What is the surrogate light chain made up of?

Answer 49

It is made up of two invariant proteins called VpreB and λ5

Question 50

More than 40% of the total proteins produced by a plasma cell are:

Answer 50

antibodies

Question 51

Ensures that one B cell will react with only one antigenic determinant and will produce antibodies to only that antigen:

Answer 51

allelic exclusion

Question 52

What are the signal transduction molecules on Pro-B cells?

Answer 52

Ig-alpha and Ig-beta

Question 53

What is the most important cytokine for T and B cell development?

Answer 53

IL-7

Question 54

If we see IgD expressed on a B cell, at what developmental stage is that B cell?

Answer 54

Mature B cell

Question 55

At which stage of B cell development do we no longer see TdT?

Answer 55

Precursor B cell

Question 56

Made up of 2 invariant proteins called VpreB and lambda-5:

Answer 56

surrogate light chain

Question 57

This is a process that attempts to rescue a self-reactive B cell from undergoing apoptosis:

Answer 57

Receptor editing

Question 58

Full maturation of a B cell is signaled by the coexpression of ____ and ____ on the cell surface.

Answer 58

Full maturation of a B cell is signaled by the coexpression of **_IgM_** and **_IgD_** on the cell surface.

Question 59

Where to Helper T cell-B cell interactions occur?

Answer 59

at the junction of the cortex and paracortex