B Cell Development

Question 1

what are the stages of B cell development?

Answer 1

• pre-pro
• pro-B
• pre-B

Question 2

what do the spontaneous recombination events generate during the development of B cells?

Answer 2

generates IgM BCR with diverse antigen-combining sites

Question 3

where do immature B cells travel once released from the bone marrow?

Answer 3

spleen

Question 4

what is elimination of self-reactive B cells?

Answer 4

involves multiple checkpoints to identify and remove or inactivate B cells that recognize “self-antigens” so that cells only react to “non-self antigens”

Question 5

explain the methods of elimination of self-reactive B cells?

Answer 5

• receptor editing: modify the 3D structure of binding sites that initiates a new round of VJ recombination
• deletion: killing off cells
• shut down function: anergy

Question 6

in the spleen the B cells undergo two transitional stages which are ?

Answer 6

T1 (negative selection) and T2 (maturation with IgD)

Question 7

explain what the T1 negative selection stage is?

Answer 7

B cells with receptors that react with self molecules encounter self antigens and are deleted and the remaining cells transit to T2

Question 8

explain what the T2 maturation with IgD is?

Answer 8

T2 B cells fully mature and express high levels of IgD on their surface in addition to IgM (called B2 cells)

Question 9

what is BAFF?

Answer 9

b cell activating factor that provides a survival signal during T2 stage

Question 10

where do B cells go after the T2 stage?

Answer 10

• some stay in follicles of the white pulp of the spleen
• some migrate via blood yo peripheral lymphoid organs (follicular b cells)

Question 11

what happens in the spleen when a B lymphocyte is stimulated by an antigen aka the Antigen- Dependent Phase?

Answer 11

C-region gene expression changes as it matures and proliferates under help from T helper cells and the B cells switch their isotypes to express IgG, IgA or IgE

Question 12

where do mature B cells take up residence?

Answer 12

follicle of the lymph nodes

Question 13

what can mature naive B cells undergo/develop into when they come in contact with an antigen in the lymph nodes ?

Answer 13

• somatic hypermutation which results in B cells producing antibodies with increased affinity for the antigen
• isotype switching with help from T helper cells
• differentiation into plasma blast then plasma cells
• memory B cell

Question 14

what do plasma cells secrete?

Answer 14

large numbers of antibody molecules but they loose their cell surface immunoglobulin

Question 15

when an antibody is produced by clonal expansion of a single B cell, the five classes of antibodies have the same what? different what?

Answer 15

• same antigen binding specificity V region
• different constant regions on the heavy chains

Question 16

what are the steps of class switching or isotype switching?

Answer 16

1. initial activation of B cell by antigen which presents it to the T helper cell
2. T helper cell is activated by its CD40 ligand binding to CD40 receptor on B cell which causes release of cytokines
3. cytokines released by the T-helper cells guide the B cell in choosing which constant region of the antibody to switch to

Question 17

what are the differences between he membrane bound form and secreted form of Ig?

Answer 17

MBF: serves as a single receptor, has cytosolic and hydrophobic segment

SF: no cytosolic segment and have a hydrophilic region

Question 18

what are B-1 cells and where are they found?

Answer 18

a minor subtype of B cells derived from embryonic precursors found in the peritoneal cavity

Question 19

what are some characteristics of B-1 cells?

Answer 19

• capable of self renewal
• do not have IgD
• produce IgM antibodies to carbohydrates without T cell help (T- independent)