Immunology 03 Antigen Receptors And Generation Of Antibody/tcr Diversity

Front 1

Describe the recognition mechanisms of innate immunity

Back 1

-Rapid response (hours)
-Fixed
-Limited Number of Specificities
-Constant during response

Front 2

Describe the recognition mechanisms of adaptive immunity

Back 2

-Slow response (days to weeks)
-Variable
-Numerous highly specific specificities that improve during response

Front 3

What is the adaptive immune response?

Back 3

The response of antigen-specific lymphocytes to antigen, including the development of immunological memory

Front 4

What mediates the adaptive immune response?

Back 4

The clonal selection of antigen-specific lymphocytes

Front 5

What are the highly variable recognition molecules of adaptive immunology?

Back 5

Immunoglobulins and T-cell receptors

Front 6

What is the relationship between an antibody and the B cell receptor?

Back 6

The antibody is the secreted form of the B cell receptor

Front 7

Explain how gene rearrangement produces diversity of antigen receptors in lymphocytes?

Back 7

V- Variable gene segment
J- Joining gene segment

There are many V and J genes. The gene rearrangement brings V and J together, which is then transcribed into an antibody. V1 can join J1 and J2, each lymphocyte expresses only a single receptor, but for the population of lymphocytes as a whole there are numerous receptors.

Front 8

Describe the structure of the immunoglobulin molecule

Back 8

It is made up of 2 identical heavy chains and 2 identical light chains. The antibody molecule has 2 functional domains.

There is a flexible hinge that allows it to bind with both arms to antigens on the surfaces of pathogens. The part that binds the antigen is the Fab (Fragment antigen binding) fragment, and the other is the Fc (Fragment crystallizable).

Front 9

What are HV regions?

Back 9

Hypervariable regions. The HV regions of the antibody V domains lie in discrete loops at one end of the domain structure. These loops contribute much of the antigen specificity of the antigen-binding site.

Front 10

What are the forces that hold together the antigen:antibody complex?

Back 10

These are non-covalent forces

Electrostatic- strogest- attraction between opposite charges
Hydrogen Bonds- hydrogen shared between electronegative atoms (N,O)
Van der Waals forces- subatomic force- fluctuations in electron clouds around molecules oppositely polarized neighboring atoms.
Hydrophobic forces- hydrophobic groups interact unfavorably with water and tend to pack together to exclude water molecules. This attraction also involves Van der Waals forces.

Front 11

What are the 5 classes of immunoglobulin molecule?

Back 11

IgG, IgM, IgD, IgA, IgE

Front 12

What are the first two classes of immunoglobulin expressed on newly developing B cells?

Back 12

IgM and IgD

Front 13

How does a naive B cell produce IgM vs IgD?

Back 13

Different splicings of the RNA transcript

Front 14

How are the constant regions of immunoglobulins encoded?

Back 14

Through exons. This is transcribed at the RNA level then spliced to an mRNA then translated.

Front 15

What are the two methods by which antibodies can act? Explain them.

Back 15

Neutralization and opsonization

Antibodies bind to antigens in the blood stream or body fluids. They kind bind to toxins, preventing the toxins from binding to the cell. Antibodies can opsonize bacteria. Neutralization works for bacterial toxins and opsoninzation works for bacteria in extracellular space. Some of the antibodies generating the response bind to complement receptors and then the complement system helps destroy the antigen.

Front 16

What is IgG involved in? IgM? IgE?

Back 16

IgG is often involved in opsonization. IgM activates the complement system. IgE is the principle molecule of allergies. IgE bound to mast cells releases histamine.

Front 17

Explain the production of a mouse monoclonal antibodies

Back 17

B cells from mouse immunized with antigen are mixed with myoloma cells. These cells fuse. The fused cells are grown in a drug-containing medium where only the hybrid cells live. These are then selected for an antigen-specific hybridoma.

Front 18

What are the four types of therapeutic monoclonal antibodies?

Back 18

Mouse, chimeric, humanized, human

Front 19

Explain chimeric monocolonal antibodies

Back 19

In these only the variable region is from the mouse

Front 20

Explain highly variable monoclonal antibodies

Back 20

In these only the highly variable region is from the mouse

Front 21

How are human monoclonal antibodies obtained from a mouse?

Back 21

The human immunoglobulin loci are put into the mouse and then the mouse starts to make them

Front 22

What is the similarity between the antibody and the T-cell receptor?

Back 22

The T-cell receptor resembles the Fab region of the antibody

Front 23

What are the two light chain loci?

Back 23

The lambda and the kappa

Front 24

How are variable region genes constructed in the light chain?

Back 24

The V is joined to the J region

Front 25

How are variable region genes constructed in the heavy chain?

Back 25

The D is joined to the J. Then the V is joined to the DJ.

Front 26

What is combinatorial diversity?

Back 26

The diversity obtained from pairing of random V, J, and D segments.

Front 27

How many V regions are in the kappa chain? the lambda chain? the heavy chain?

Back 27

31-36
29-33
38-46

Front 28

How many D regions are in the kappa chain? the lambda chain? the heavy chain?

Back 28

0
0
23

Front 29

How many J regions are in the kappa chain? the lambda chain? the heavy chain?

Back 29

5
4-5
6

Front 30

How many C regions are in the kappa chain? the lambda chain? the heavy chain?

Back 30

1
4-5
9

Front 31

What is RSS? What is its importance?

Back 31

Recombination Signal Sequence

RSS is a defined nuclear type sequence that consists of a heptamer and a nonamer which are always the same. Between these heptamer and nonamer there is a 12 or 23 nucleotide spacer. There are enzymes which recognize these regions specifically and then bring together these 2 DNA regions. The 23-12 rule is that one can only join these RSS sequence when there are 23 on one side and 12 on the other. The lambda chain and the kappa and heavy chain genes always have these 12 and 23 regions . The V cannot directly join to the J without the D due to the spacer rule.

Front 32

What are RAG proteins? What do they do?

Back 32

Recombination activating genes. They were cloned and defined by their ability to recombine. These RAG proteins bind to these RSS sequences . One random V segment is brought together with a random J segment and then there are enzymatic processes that generate open DNA so that the V can form with the J. In the end you have a variable region coding joint.

Front 33

What is junctional diversity? How does it occur?

Back 33

This is at the DNA level at the generation of the junctional diversity between D and J segments. The hepatmers are cut off and you eventually end up with 2 openly DNA ends that are covalently linked so that you have hairpins. An exonuclease then cuts one of the nucleotides (1 or2 upstream of the 3' end) then you generate pallendromic nucleotides. Then, in order to generate a lot of diversity there is an enzyme TdT which adds random nucleotides to these junctions. Then eventually the DNA has to be joined to make a functional protein. This is done by different enzymes. Eventually the strands are pairs and the missing nucleotides are introduced by a DNA polymerase so that in the end you get a complete joint that can eventually make proteins.

Front 34

What mediates junctional diversity?

Back 34

V(D)J recombinase (including RAG)

Front 35

Where does recombination occur?

Back 35

At RSS sequences

Front 36

What non-germline encoded nucleotides are added?

Back 36

P nucleotides, as a result of opening of the "hairpin"
N nucleotides by the enzyme TdT

Front 37

The region encoded by junctional diversity is which HV region?

Back 37

The third

Front 38

What are the three mechanisms to establish diversity of pre-immune receptors? How many different antibody specificities can be obtained with these mechanisms?

Back 38

-Combinatorial diversity (by V,D, J on the heavy chain and by V and J on the light chain)
-Junctional Diversity
-Combinatorial diversity through HC and LC combinations

10^11

Front 39

Why don't all rearrangements lead to suitable antigen-receptors?

Back 39

-Some Vh and Vl genes segments are pseudogenes.
-Junctional diversity can lead to reading frame shifts
-Junctional diversity can introduce translational stop codons.
-Some of the receptors generated are autoreactive

Front 40

What part of B-cell development is antigen independent?

Back 40

Up until the self reactive immature lymphocytes are removed through clonal deletion

Front 41

What part of B-cell development is antigen dependent?

Back 41

Binding to the antigen and proliferation and differentiation of activated specific lymphocytes to form a clone of the effector cells.