biol454 lymphocyte development 2

what are 2 main problems with VDJ gene rearrangement?

1. huge potential to generate nonfunctional gene arrangements/non functional Ag receptors

2. huge potential to generate self-Ag reactivity

how does VDJ gene rearrangement generate nonfunctional Ag receptors?

• out of frame VDJ rearrangements

• premature stop codons

how does generation of self-Ag reactivity occur from VDJ rearrangement?

• junctional diversity is not germline encoded

• potential to recognize self and cause autoimmune disease

what provides a maturation and differentiation microenvironment for B cell development?

bone marrow

B cell development

what location…

• regulates construction of an antigen receptor

• ensures each cell has only one specificity

• checks and disposes of self-reactive B cells

• exports useful cells to periphery

• provides site for antibody production

bone marrow

what are the two checkpoints for T/B cell development?

• Pre-B/T antigen receptor expression (3)

• Antigen receptor expression (5)

which steps of development are checkpoints?

2.4

B cell maturation

RAG and TDT expression occur when ? develops into ?

Pro-B into Pre-B

which stage of maturation has a recombined H chain gene and a pre-B receptor?

Pre-B cell

which stages of maturation have no response to antigens?

stem cell, pro-b, pre-b

name the stages of maturation for B cells (start to finish)

1. stem cell

2. pro-B cell

3. pre-B cell

4. immature B cell

5. mature B cell

what is an unproductive gene rearrangement?

rearrangements that do not give rise to functional proteins

what is a productive gene rearrangement?

gives rise to functional protein (full length chain)

for gene rearrangements, in what scenario does the B cell precursor die (due to apoptosis)

both rearrangements on homologous chromosomes are unproductive

(t/f) only successfully rearranged heavy chains can associate with V pre-B receptor

true

Pre-BCR is made up of what two components?

V pre-B and heavy chain

Pre-BCR is expressed on the surface of what lymphocyte?

Pre-B cell

which cell receptor is responsible for…

• inhibition of H chain recombination

• proliferation of pre-B cells

• stimulation of light chain recombination

• shutting off surrogate light chain transcription

pre-B cell

what lymphocyte is this?

pre-BCR

(t/f) no part of pre-BCR is similar to BCR

false, the V region is “similar” to BCR

what happens when VpreB makes surface pre-BCR dimerize?

it sends a signal

what causes…

1. survival, proliferation

2. decreased VDJ gene rearrangement

   1. HC allelic exclusion

3. decreased pre-BCR and IL-7 signaling

4. increased light chain VJ gene rearrangement

self-aggregation/cross-linking induced signaling of pre-BCR

B cell development in bone marrow requires what?

stromal cells

what growth factors (cytokines) are produced by stromal cells? what are they recognized by?

• stem cell factor (SCF) - Kit on B cell precursor

• IL-7 - stimulates pro and pre-B cells via IL-7 receptor

in a common lymphoid progenitor cell, what are the adhesion dependent contacts? (for the CLP and stromal cell)

CLP: VLA-4

stroma: VCAM-1

what lymphocyte recognizes SCF on the stroma with a Kit receptor?

early pro-B cell

expression of what receptor turns of rearrangement of H chain genes?

pre-B cell receptor (pre-BCR)

when expressed on cell surface, what turns of RAG genes?

BCR

signaling takes place via ? and ?

Iga,, IgB

B cell development

at what stage of maturation does heavy chain rearrangement stop and light-chain rearrangement begins?

large pre-B cell

B cell development

at what stage of maturation does light-chain rearrangement stop?

immature B cell

B cell development

at what stage of maturation does heavy chain rearrangement begin?

early pro-B cell

monospecificity

• 1 functional IgH allele

• 1 functional IgL allele (kappa or lambda)

• 1 antigen specificity

polyspecificity

• 2 function IgH alleles

• 6 functional IgL alleles

• 12 different antigen specificities

allelic exclusion

property of expressing only one of two Ig alleles

what mechanism is this?

• once a functional heavy chain is made, the pre-BCR can assemble and send signals

• Rag1 and Rag2 proteins are redirected away from IgH locus

• Rag1/2 is turned off when a functional light chain is made

mechanism for allelic exclusion

how does allelic exclusion enhance antibody efficiency?

it ensures one B cell and its clonal progeny will make homogenous antibodies with two identical binding sites

what stage of maturation is this?

• RAG expression

• Ig DNA/RNA: recombined H chain gene, kappa or lambda genes (VJ), mu, kappa, or lambda mRNA

• Ig expression: membrane IgM (mu or kappa or lambda light chain)

• response to antigen: negative selection (deletion), receptor editing

immature B

for rearrangement of (heavy/light chain), several rounds of rearrangement until productive

light

(t/f) about 85 pct of pre-B cells have productive L chain rearrangement

true

checkpoint (1/2) negative selection of B cells and receptor editing

checkpoint 2

what situation causes this to occur:

• BCR signals through Ig-alpha and Ig-beta to turn on RAG and start rearrangement of lambda light chain to try and generate an antibody with lower affinity for self antigen

BCR with functional H and L chain sees self-protein

receptor editing occurs when…

• BCR with functional H and L chain sees self-protein

• signals through Iga and Igb to turn on RAG to rearrange lambda-light chain to generate antibody with lower affinity for self antigen

order of rearrangement for human Ig (ab) locus

1. heavy chain locus

2. kappa light chain locus

3. lambda light chain locus

H-chain gene rearrangement occurs in which stages of maturation for B cells?

early and late pro-B cell

in B cell development, at which stage of development does L chain gene rearrangement occur?

pre-B cell

productive kappa gene on either the first or second chromosome results in the cell expressing…

mu/kappa IgM

productive lambda gene on the first or second chromosome results in the cell expressing…

mu/lambda IgM

what happens if unproductive rearrangement occurs after rearrangement on BOTH chromsomes for kappa AND lambda?

apoptosis

(t/f) the L chain is rearranged before H chain

false, heavy then light

B cells can continue to rearrange IgL genes, try to change L chain, lose self reactivity

receptor editing

B cells can die

clonal deletion or negative selection

B cells can become refractory to activation

clonal anergy

what event is:

• essential for B cell development

  • only happens when there is a successful heavy chain associating with VpreB

pre-B cell receptor dimerization

B cells have several opportunities to rearrange their light antigen receptors. What is the order they are rearranged in?

1. first chromosome - kappa

2. second chromosome - kappa

3. first chromosome - lambda

4. second chromosome - lambda

signaling of immature BCR results in…

deletion or receptor editing

? is essential to the clonal nature of immunity

allelic exclusion

When mature B cells leave the bone marrow, what is expressed on their membrane?

IgM and IgD

What happens when a BCR binds specific Ag and is activated?

It makes mAbs

In Pre-B cells, pre-BCR signaling induces

developmental progression → light chain rearrangement

When an immature B cell receives BCR signal (self antigen), what occurs?

deletion and/or light chain receptor editing

When a mature B cell receives BCR signal (foreign antigen), what occurs?

cell activation

a thymus is larger in a fetus or an adult?

fetus

T cell precursors move from what two locations to develop?

bone marrow to thymus

mature T cells leave the thymus in ?, move to secondary lymphoid organs, circulate between ?, secondary lymphoid tissues and lymph

blood

the thymus contains… (2)

• immature T cells (thymocytes)

• dense network of epithelial cells (thymic stroma)

(t/f) In the absence of thymus, T cells do not develop

true

what is a nude mouse?

phenotype due to mutation in a gene required for terminal epithelial cell differentiation

immature thymocytes do not express… (3)

CD4, CD8, or TCR

What is a double negative lymphocyte?

CD4- CD8- cells

stage of maturation: ?

proliferation: late half

RAG expression: early half

TdT expression: no

TCR DNA, RNA: recombined beta chain gene, beta chain mRNA

TCR expression: Pre-T receptor (beta-chain/pre-T alpha)

surface markers: c-kit+, CD44- CD25+

anatomic site: thymus

response to antigen: none

Pre-T

Which stages of maturation for the T-cell have no response to antigen?

stem cell, pro-t, pre-t

which stage of maturation…

proliferation: no

RAG: yes

TdT: no

TCR DNA, RNA: recombined beta, alpha chain genes; beta and alpha chain mRNA

TCR expression: membrane alpha-beta TCR

surface markers: CD4+/CD8+/TCR

anatomic site: thymus

response to antigen: positive and negative selection

double positive

which stage of maturation is…

proliferation: no

RAG/TdT expression: no

TCR DNA, RNA: recombined beta, alpha chain genes; beta alpha chain mRNA

TCR expression: membrane alpha-beta TCR

surface markers: CD4+CD8-, CD4-CD8+

anatomic site: thymus

response of antigen: no

single positive immature T cell

what stabilizes the peptide/MHC TCR complex?

co-receptors

what binds to the a3 domain (Ig-like) of Class I

CD8

what binds to b2 domain (Ig-like) of class II

CD4

without … there is no T cell activation

co-receptor MHC engagement

if there is … there will be no positive selection of CD8 single positive T cells

no MHC1

if there is … then there will be no positive selection of CD4 single positive T cells

no MHC2

negative selection purges cells of high binders for…

self-MHC

CD(4/8) helper T cell co-receptor

CD4

CD(4/8) cytotoxic T cell co-receptor

8

T cells in the periphery have strong reaction against … with peptides from transplant

allogenic MHC (non-self-MHC alleles)

TCR specific for self-MHC/foreign-peptide may cross-react strongly with… (2)

1. peptide portion of nonself-MHC/peptide complex

2. MHC portion of the nonself-MHC/peptide complex