Adaptive Antigen Recognition in the Immune System

Question 1

B cell activation overview

Answer 1

No need for APC to be activated.
Ags from B cells can be soluble or cell-associated.
Activated B cells are transformed to plasma cells or memory cells.

Question 2

Plasma cells are found in:

Answer 2

Lymphoid organs

Question 3

T cell activation overview

Answer 3

T cells require MHC.

T cells become activated when TCR recognizes Ag presented by APC on MHC.

Question 4

Signaling structures in BCRs (2)

Answer 4

alpha and beta subunits

Question 5

Signaling in TCRs (2)

Answer 5

CD3 and zeta subunit.

Question 6

Most Abs are found in the ______ in electrophoresis

Answer 6

The third slowest migrating group of globulins. (alpha, beta, gamma). Called y-globulins.

Question 7

Abs have how many polypeptide chains? How are they bound?

Answer 7

4. Two heavy and two light.

Bound by disulfide bridges and noncovalent interactions.

Question 8

What enzyme cleaves IgG?

Answer 8

Papain

Question 9

How does pepsin cleave Ig?

Answer 9

Leaves Fabs attached but lyses the Fc region.

Question 10

How are the types of Abs determined? (i.e. IgM, IgG, IgA. etc).

Answer 10

based on the different H chains.

Referred to as m, d, g, e, a.

Question 11

Types of L chains (2):

Answer 11

k and lambda.

Each weigh 23 kDa.

Question 12

5 Ig classes:

Answer 12

IgG
IgD
IgE
IgA
IgM

Question 13

The higher the binding constant:

Answer 13

The less likely the Ab is to dissociate from the Ag.

Question 14

Affinity of primary response vs memory response:

Answer 14

Primary response is much lower than memeory response.

Question 15

Valence of an Ab

Answer 15

The maximum number of antigenic determinants with which it can react.
Ex: IgG has 2 Fab regions therefore it can bind 2 Ags = valence of 2.

Question 16

What is avidity? And what is it dependent on?

Answer 16

The measure of the overall strength of the Ab-Ag complex.
It is dependent on affinity of the Ab for the Ag.
Valence of both Ag and Ab.

Question 17

HAT medium includes (3)

Answer 17

Hypoxanthine
Aminopterin
Thymidine

Question 18

How are myeloma cells that did not hybridize killed in the assay?

Answer 18

They lack HGPRT gene are cannot perform purine salvage. This causes only hybrid cells to survive in the HAT medium.

Question 19

Structure of the TCR

Answer 19

Includes alpha and beta TCR noncovalently linked to CD3 and zeta proteins.

Question 20

CD4 has (3):

Answer 20

4 extracellular Ig-like domains
Hydrophobic transmembrane region
Highly basic cytoplasmic tail 38 AA long.

Question 21

CD2 is composed of 2 related chains called:

Answer 21

CD8a and CD8b

Question 22

CDa and CDb have (3):

Answer 22

Single Ig-like domain
Hydrophobic transmembrane region.
Highly basic cytoplasmic tail 25 AA long.

Question 23

CD8 interacts with what on the MHC I?

Answer 23

B2 microglobulin

Question 24

Antigen binding occurs much faster in:

Answer 24

Ig than TCR

Question 25

Steps in maturation of Lymphocytes (4)

Answer 25

1. Commitment of hepatopoietic progenitors to the B or T cell lineage. 2. Proliferation of the progenitors. 3. Rearrangement and expression of the Ag receptor. 4. Selection events to preserve and expand cells that express useful receptors.

Question 26

BCR genes Ig H chain locus is on: Ig k chain locus is on: Ig y chain locus is on:

Answer 26

Chromosome 14 Chromosome 2 Chromosome 22

Question 27

TCR genes TCR beta chain locus is on: TCR alpha chain locus is on:

Answer 27

Chromosome 7 | Chromosome 14

Question 28

Allelic exclusion in Abs

Answer 28

Only 1 of the L chain and H chain alleles is expressed in a single B cell or T cell (either maternal or paternal). Bceuase there are so many B/T cells, there is essentially an equal expression from maternal and paternal allotypes.

Question 29

Rag1 and Rag2 function

Answer 29

Genes that code for recombination enzymes that act on DNA/RNA to increase diversity of the Ag receptor. Restricted to B and T cells only during development.

Question 30

Gene segments for the H chain (4):

Answer 30

``` V-variable D-diversity J-joining C-constant Each B cell generates its own V-D-J sequence making it unique. ```

Question 31

How is BCR diversity achieved? | H chain

Answer 31

D and J chosen first V chosen second C chosen last There is a test to determine "productive rearrangement".

Question 32

Junctional diversity does what?

Answer 32

Further increases the variety of Ags a TCR or BCR can recognize.

Question 33

Junction diversity mechanism

Answer 33

RAG cleaves hairpin loop and adds new N and P nucleotides to increase diversity.

Question 34

Checkpoint #1 of lymphocyte development: | Checkpoint #2 of lymphocyte development:

Answer 34

1: After the production of the first polypeptide chain of the 2 chain Ag receptor. 2: Occurs after production of second polypeptide chain. Both checkpoints ensure that the lymphocyte has complete successful rearrangement.

Question 35

Pre-BCRs contain (1):

Answer 35

Ig m heavy chain and surrogate light chain.

Question 36

Pre-TCRs contain (1):

Answer 36

TCR beta chain

Question 37

In-frame rearrangements cause:

Answer 37

The cell to continue to develop. | 30%

Question 38

Out-of-frame rearrangements cause:

Answer 38

Pre-Ags not to be expressed and cells undergo apoptosis.

Question 39

Positive selection

Answer 39

B and T cells with functional pre-Ag receptors proceed to express genes encoding the second chain of the BCR or TCR. These cells will reocgnize MHC molecules but not themselves.

Question 40

Negative selection

Answer 40

Eliminates harmful T and B cells whose Ag receptors bind to Ags present in bone marrow or thymus. Harmful T cells undergo apoptosis, but harmful B cells undergo a seoncd attempt in rearrangement of Ig gene.

Question 41

Receptor editing

Answer 41

When B cells get another chance to rearrange their Ig gene. If editing fails, B cells die.

Question 42

B cells developing from the fetal live-derived stem cells give rise to:

Answer 42

B-1 lineage

Question 43

B cells that arise from bone marrow precursors after birth give rise to:

Answer 43

B-2 lineage

Question 44

B-1 cells overview

Answer 44

Develop from fetal liver-derived HSCs. Limited BCR diversity as TdT is not expressed in liver. Spontaneously secrete IgM. They also secrete the most IgM in early phases of infection.

Question 45

B-2 cells overview

Answer 45

Develop from bone marrow. Relocate to the spleen. Immature B-2 B cells diferentiate into MZ B-2 cells or FO B-2 cells.

Question 46

FO B-2 cells are:

Answer 46

Recirculating lymphocytes. Only FO B-2 cells are dependent upon T cell activation and develop into long-lived plasma and memory cells.

Question 47

MZ B-2 cells are:

Answer 47

Abundant in spleen and in the LNs. Self renewing. Function independent of T cell help.

Question 48

Negative selection of T cells occurs in:

Answer 48

Thymic medulla

Question 49

Positive selection of T cells occurs in:

Answer 49

Thymic cortex.

Question 50

What gene is missing in the light chain biosynthesis?

Answer 50

D

Question 51

tdT function

Answer 51

To add N nucleotides in junctional diversity.