Lymphocyte Development - Johnson

Question 1

All lymphoid neoplasms are derived from transformed single cells and are thus ______.

Answer 1

Clonal

Question 2

B and T cells undergo antigen receptor gene rearrangment, which almost always occurs (before / after) transformation.

Answer 2

Before.

Thus, clonal malignant B or T cells can be ID’ed by thier unique antigen receptors.

Question 3

The central/primary lymphoid tissue and site of B cell maturation is the __________.

The central/primary lymphoid tissue and site of T cell maturation is the __________.

Name three examples of peripheral lymphoid organs.

Answer 3

B-cells: Bone Marrow

T-cells: Thymus

Peripheral:

1. LNs
2. Spleen
3. Musocal/cutaneous lympoid tissues (GALT, MALT, etc.)

Question 4

Which lymphocyte’s antigen receptor is MHC-restricted?

Which lymphocyte receptor can recognize not only proteins but carbohydrates, lipids, nucleic acids, etc., as well?

Answer 4

MHC: T-cell

Many ligands: B-cell (T-cells are peptide:MHC only)

Question 5

Which lymphocyte receptor can recognize not only linear epitopes but conformational (structural) ones as well?

Answer 5

BCRs/Igs

Think about it - TCRs only recognize MHC:peptide, and those peptides have always been cleaved up and processed by cellular machinery and thus have a linear structure.

Question 6

The antigen-recognizing portion of the BCR is a membrane-bound Ig, composed of what two parts?

The signal-transducing portion of the BCR is composed of what two proteins?

Answer 6

Recognition: heavy & light chains of the Ig

Transduction: Ig_alpha and Ig_beta

Question 7

The TCR is a composed of what?

What are the two signal-transducing proteins associated with the TCR?

Answer 7

TCR: Variable regions of alpha and beta chains

Transduction: CD3 and zeta chain

Question 8

How many isotypes or classes of BCR/Ig are there? What are they?

How many types of Ig light chains are there? What are they?

Answer 8

BCR: 5

• IgA
• IgD
• IgE
• IgG
• IgM

LC: 2

• lambda
• kappa

Question 9

1. Is the Ig variable region derived from the light or heavy chain?
2. How many regions of hypervariability does the Ig variable region contain?
3. What do these regions represent?

Answer 9

1. Trick question (sorry) - variable region is partly comprised of both the light & heavy chains
2. Three
3. These are the **epitope **contact sites in the antigen binding site of the receptor/Ig

Question 10

Which secreted Ig’s form multimers, and what size multimers do they form?

Answer 10

IgA: monomer, dimer, trimer

IgM: pentamer

Question 11

What is an anti-allotypic antibody?

People with what disease often generate these types of antibodies?

Answer 11

• Typically, an antibody directed against the constant region of other antibodies (e.g. anti-IgG Ab) will react with the same isotype of Ig from any human.
• Anti-allotypic Abs are directed against other Abs, but can differentiate between contstant regions from different individuals based on small polymorphisms (a.k.a. allotypes) that exist in the constant region.
• Common in pts with rheumatoid arthritis

Question 12

What is an anti-idiotypic antibody? What are they useful for?

Answer 12

• An antibody directed against the variable region (a.k.a. idiotype) of another antibody.
• Can be used to identify B cells from an individual with a B cell tumor, because the malignant B cells will be from a single clonal population and will thus share the same variable region.

Question 13

Are Ig domains found in BCRs? TCRs?

Answer 13

Ig domains are found in both BCRs and TCRs. The domain was initially described in Igs, hence the name. But the domain is common to other molecules as well, including the TCR.

Question 14

What size peptide does a CD4+ T-cell TCR recognize?

What size peptide does a CD8+ T-cell TCR recognize?

Answer 14

CD4: 14-24aa

CD8: 8-10aa

Question 15

Which have a higher affinity for their given antigen: Igs or TCRs? During an immune response, does the affinity of Igs or TCRs for their given antigen increase?

Answer 15

Igs, often by several orders of magnitude.

Igs show increasing affinity during an immune response (somatic hypermutation!), TCRs have static affinity.

Question 16

Differentiate **affinity **and avidity.

Answer 16

Affinity: strength of a single binding interaction

Avidity: the combined strength of multiple interactions involved in a recongition event (e.g. MHC-TCR interaction plus simultaneous coreceptor interactions)

Question 17

In maturing B cells, rearrangement of the (light / heavy) Ig chain occurs first.

In maturing T cells, rearrangement of the (alpha / beta) TCR chain occurs first.

Answer 17

B cells: heavy chain

T cells: TCR beta chain

Question 18

Fill in the blanks:

The variable region of the heavy chain (Ig HC or TCRbeta) is composed of ___ gene segments, which are named ______.

The variable region of the light chain (Ig LC or TCRalpha) is composed of ___ gene segments, which are named ______.

Answer 18

Heavy: 3 gene segments: V, D, and J.

Light: 2 gene segments: V and J.

(Mnemonic: the **heavy **chain is Dense.)

Question 19

Describe the order of gene recombinations in the heavy chain.

Describe the order of gene recombinations in the light chain.

Answer 19

Heavy:

1. D + J
2. V + DJ
3. C + VDJ

Light:

1. V + J
2. C + VJ

(C segment = constant region)

Question 20

Contrast combinatorial vs. **junctional **diversity.

Answer 20

Combinatorial: The number of possible V-(D)-J combinations during somatic recombination

Junctional: Additional divesity provided by removal or addition of nucleotides in the already-recombined gene segments.

Together, the two types of diverty make up the total potential repertoire of antigenic recognition diversity.

Question 21

What is allelic exclusion?

Answer 21

A mechanism during lymphocyte receptor development that ensures clonal specificity.

As soon as a viable (in-frame) transcript is produced by somatic recombination, no further recombination of that chain will occur. A rearrangement is first attempted by one chromosome:

• If that succeeds, recombination is prevented in the second chromosome.
• If that fails, recombination is attempted by the second chromosome.
• If both fail, the cell will die (lack of positive selection).

Question 22

What function are the RAG-1 and RAG-2 enzymes responsible for? What condition results when they are mutated / dysfunctional?

Answer 22

RAG-1 and RAG-2 are the VDJ recombinase enzymes.

Deficiency results in autosomal SCID.

Question 23

The following diseases are caused by deficiencies of what?

1. XLA
2. autosomal SCID
3. X-linked SCID
4. DiGeorge snydome

Answer 23

1. Btk
2. RAG, ADA, or PNP
3. common gamma chain
4. thymus (lack thereof)

Question 24

Deficiencies of the following enzymes / structures will cause what dieases?

1. Btk
2. ADA
3. common gamma chain
4. PNP
5. thymus
6. RAG

Answer 24

1. XLA
2. autosomal SCID
3. X-linked SCID
4. autosomal SCID
5. DiGeorge syndrome
6. autosomal SCID

Question 25

What cytokine is critical for the initial development of pro-B and pro-T cells?

Answer 25

IL7

Question 26

What is the 1st checkpoint of lymphocyte selection? What is the 2nd checkpoint?

Answer 26

1st: Does the cell express a viable pre-lymphocyte receptor? 2nd: Does the cell express a viable complete lymphocyte receptor?

Question 27

During lymphocyte development, what will result from: 1. Weak self:antigen recognition? 2. No self:antigen recognition? 3. Strong self:antigen recognition?

Answer 27

1. Weak: Survival via positive selection 2. No: Death by neglect (lack of positive selection) 3. Strong: Death by negative selection

Question 28

What stage of receptor generation / somatic recombination are the following B-cell precursors at? 1. Stem cell 2. Pro-B cell 3. Pre-B cell 4. Immature B cell 5. Mature B cell

Answer 28

1. germline DNA 2. germine DNA 3. Recombined H chain gene (VDJ) 4. Recombined heavy (VDJ) and light (VJ) chain genes; immature IgM 5. Alternative splicing of primary transcript as the cell matures; membrane IgM and IgD

Question 29

Is the rearrangement of T and B cell antigen receptors random or driven by antigens?

Answer 29

Random

Question 30

Describe whether the following T-cell precursors express CD4 and/or CD8 coreceptors: 1. Pro-T cells 2. Pre-T cells 3. Immature T cells 4. Mature T cells

Answer 30

1. Pro: CD4-, CD8- (Double Negative) 2. Pre: CD4-, CD8- (Double Negative) 3. Immature: CD4+ AND CD8+ (Double Positive) 4. Mature: CD4+ OR CD8+ (Single Positive)

Question 31

During thymic development, do T cells travel from the cortex to the medulla as the develop, or from the medulla to the cortex?

Answer 31

From the cortex to the medulla.

Question 32

What are Hassall's Corpuscles and where are they found?

Answer 32

* Found in the thymic medulla * Composed of a central mass, consisting of one or more granular cells, and of a capsule formed of epithelioid cells * Function remains unclear (Likely unimportant - just want you all to not be thrown for a loop if the term were to pop up)

Question 33

During T-cell selection in the thymus, expression of a variety of MHC:self-peptide on the surface of thymic dendritic cells is driven by what gene?

Answer 33

AIRE

Question 34

# Parts of the Ig molecule Identify the following sections of the immunoglobulin molecule: 1. The green peptide chains 2. The red + blue peptide chains 3. The area within the blue box 4. The area referred to by the green box 5. The area referred to by the red box 6. The area marked with a star 7. The peptide structure indicated by the #

Answer 34

(See image below) 1. Light chain 2. Heavy chain 3. Antigen-binding site 4. Fab region 5. Fc region 6. Hinge 7. Ig domain