Thrush - B cell activation

Question 1

B cell dev is divided into two major phases:

Answer 1

1. Ag independent phase: takes place in BM. Noted by Ig gene rearrangement
2. Ag - dependent phase: upon recognition of Ag, B cell: proliferates, becomes plasma cell/memory cell –> class switches

Question 2

Describe B cell development

Answer 2

1. Ag independent phase: Ig gene rearrangement = Ag specific B cells.
2. movement to periphery: contact Ag, then proceed. 90% B cells die; self reactive cells apoptose –> clonal deletion.
3. Ag dependent phase: Along with T cell help, B cells will dev into plasma cells or memory cells and can class switch

Question 3

what are classic B cell markers

Answer 3

CD19, CD20, CD45R

Question 4

A ___ cell is not committed to becoming a B cell.

Answer 4

stem

Question 5

___alpha and ___ beta are signaling molecules for antibody.

Answer 5

Ig; Ig

Question 6

What do the pro- B cell consist of

Answer 6

1. heavy chain rearrangement
2. CD19, CD20, CD45R
3. Igalpha, Igbeta
4. RAG/1 RAG/2
5. Tdt expression

Question 7

what does the pre-B cell consist of

Answer 7

Heavy chain with surrogate light chain on B cell surface

*no Tdt expression

Question 8

describe membrane expression

Answer 8

surrogate light chain allow heavy chain to go to surface of B cell. When they interact with bone marrow stromal cells. Ig alpha and Ig beta go in and tell them to start light chain

Question 9

what is receptor/light chain editing

Answer 9

an attempt to make a self reactive/bad Ab into a good one.

Question 10

____ B cell is the one that expresses IgM and IgD and begins Ag ____ phase and B cell activation

Answer 10

Mature/naive; dependent

Question 11

After Ig heavy gene rearrangement, it associates with ____ ____ chain and binds stromal cell marker, then ___ stop and light chain starts. It cannot rearrange other H- chain alleles. This is known as ___ ____

Answer 11

surrogate light; IgH; allelic exclusion

Question 12

In bone marrow B cell isn’t there by itself. Its also interacting with ____ cells

Answer 12

stromal

Question 13

Without Ag stimulation B cell will die. _____ ______Ags need T cell help

Answer 13

Thymus dependent; with the help of cytokines and other proteins

Question 14

Thymus independent Ags are divided into two types:

Answer 14

TI-1: bacterial cell wall components (LPS); not Ag specific; polyclonal B cell activators.

TI-2: repetitious cell wall components (polysaccharides); Ag specific!

Question 15

What are two signals for B cell activation

Answer 15

1. Ab binding to Ag: need crosslinking of mIg; single epitope Ags are not effective. Need Igalpha and beta to send signal to nucleus.
2. CD40 interacting with CD40L which is on T cells which means they have been activated too.
   - Cytokines can also serve as 2nd signal

Question 16

____sends second signal to B cell to help activate it

Answer 16

CD40

Question 17

Ig alpha and Ig beta are responsible for _____ to be phosphorolated which causes a signaling cascade. Signaling results in changes in gene expression

Answer 17

ITAM = immunoreceptor tyrosine based activation motif

Question 18

____ is the ligand binding domain and the signal transducing molecules

Answer 18

BCR

Question 19

When CD21 binds to ____ it causes a conformational change to CD21 which causes CD19 to send a signal to activate B cell. ____ sends a negative signal to the B cell and is considered a ____

Answer 19

C3d; CD22; ITIM

Question 20

Summarize B cell activation

Answer 20

1. Ig binding to Ag causes crosslinking. You get Igalpha and beta signaling as well as CD40 and CD40L, or CD19 and 21 if complement proteins are present.
2. Then you get changes in gene expression.
3. Internalization of Ig/Ag complex to destroy it.
4. Ag presentation to T cells then you get more co stimulation of B cell cell
5. B cell differentiation: class switching, memory cell and plasma cell production

Question 21

What are two signals that T cells need.

Answer 21

1. TCR- Ag/MHC

2. CD28 - B7

Question 22

___ is present when you get a switch to IgE

Answer 22

IL-5

Question 23

What are unusual B cells. Where are they located?

Answer 23

B1 B cells that express CD5 on their surface. They have limited diversity. Then tend to use V region genes closes to the D locus at the end. They have a few choice to use. They are in pleural and peritoneal cavities. They have low affinity and high rate of cross reactivity (polyspecificity). They usually bind to polysacchrides. They dont class switch or have T cell help and self proliferate in periphery without Ag stimulation and are likely to dev into cancer.

Question 24

what is a T cell marker

Answer 24

CD5

Question 25

Abs from B1 B cells often called _____ antibodies.

Answer 25

natural

Question 26

What is the effector function of the B cell of the antibody?

Answer 26

1. Primary response: when a naive B cell first sees its Ag: characerized by IgM production, slower response, during/after this response, B cells class switch, doesnt have to have T cell help but it works better with it. 2. Secondary response: Memory response; production of IgG or other isotypes; affinity maturation; quicker response; needs T cell help

Question 27

where is B cell getting activated

Answer 27

Lymph tissue/ lymph nodes

Question 28

where is the area where mature B cell development occurs

Answer 28

germinal center

Question 29

____ dendritic cells trap antigen but dont internalize it. Its not a traditional antigen presenting cell bc they dont express MHC class II

Answer 29

Follicular

Question 30

What are Ig/Ab functions

Answer 30

1. Pathogen neutralization 2. Complement fixation 3. antibody dependent cellular cytotoxicity 4. opsonization 5. inflammation