Lecture 9

Question 1

Differences between TCR and BCR

Answer 1

-only 1 antigen binding site—>monovalent
-always membrane bound (cannot be secreted)
-1 type of constant region–>NO istotypes/switching
-binds to antigen as a complex with a MHC molecule
-lower affinity for antigen than antibody

Question 2

What 2 distinct types of TCRs are generated?

Answer 2

-alpha & beta T cell (more abundant)
-gamma & delta (more rare)

Question 3

True or false: A T cell can express more than 1 TCR

Answer 3

False
-T cell will express only 1 TCR
-NO coexpression of alpha beta and gamma delta TCR
-1 at a time

Question 4

What are the mechanisms for diversity for T cells?

Answer 4

Before Antigen stimulation
1. Somatic recombination
2. Imprecise junction
3. Combinatorial Pairing

Question 5

True or false: Somatic hypermutation occurs in T cell development

Answer 5

False
-no somatic hypermutation, NO isotype switching, NO AID–>somatic hypermutation allows for antibody diversity–>T cells do not secrete antibodies, instead gets diversity in thymus
-there is NO change AFTER antigen stimulation

Question 6

Does the alpha chain locus have a D segment

Answer 6

No D segment–>only V and J
-similar to light chain of immunoglobulin locus

Question 7

Does the beta chain locus have a D segment?

Answer 7

Yes it has a D segment–>V, D and J segments

Question 8

What happens if someone does not have a RAG protein?

Answer 8

If no RAG protein then No B cells or T cells can be made since RAG is used in rearrangement for both types of cells

Question 9

What is severe combined immuno deficiency (SCID) syndrome?

Answer 9

When you lack B-cells and T-cells b/c no RAG
-get bone marrow transplant as treatment to re introduce RAG proteins

Question 10

In the Gamma/delta gene segments where is the delta segment?

Answer 10

In between the V & J segments of variable alpha chain
-once T cell recombines it deletes the delta segment

Question 11

What is CD3 polypeptide chains and z chain used for?

Answer 11

The transport of newly synthesized TCR to the cell surface and for the transduction of signals to the cell interior after TCR binds to specific MCH-Ag
-TCR never goes to surface if no CD3
-Once TCR is bound to antigen allows for signaling–>activates clonal expansion differentiation

Question 12

How does CD4 and CD8 coreceptors help MHC binding?

Answer 12

They bind to the MHC membrane proximal region and stabilize the TCR and MHC peptide binding

Question 13

What does CD8 bind to and make ?

Answer 13

Alpha3 domain of MHC I–>Cytotoxic T lymphocyte (CTL)

Question 14

What does CD4 bind to and make?

Answer 14

Beta2 domain of MHC II–>Helper T lymphocyte (Th)

Question 15

What does it mean for a gene to be allelic?

Answer 15

Variant of genes
-alternate forms/variants of genes
-Ex: blood type

Question 16

What does it mean for a gene to be monomorphic?

Answer 16

Only 1 version of a gene–>is the same for everyone
-Ex: RAG protein

Question 17

What does it mean for a gene to be polymorphic?

Answer 17

Multiple alleles exist in the population that can be inherited

Question 18

What is a homozygote?

Answer 18

Sets of chromosomes are the same

Question 19

What is a heterozygote?

Answer 19

Alleles are different

Question 20

What does it mean to be polygenetic?

Answer 20

Different types of genes of MHC I and MHC II
-Ex: MHC I–>HLA-A,HLA-B,HLA-C

Question 21

What does it mean to be polymorphic?

Answer 21

There are alternative forms of each MHC type (alleles) within a population–>variations of alleles
-Ex: HLA-A, HLA-A1, HLA-A2

Question 22

What is known as the most polymorphic genes?

Answer 22

MHC genes
-specifically MHC I

Question 23

What is MHC known as?

Answer 23

Human Leukocyte Antigens (HLA)

Question 24

What is a haplotype?

Answer 24

A combination of alleles on the same chromosome

Question 25

What kind of inheritence is expressed for MHC

Answer 25

Co-dominant
-both alleles for each MHC gene type are expressed

Question 26

What contributes to the diversity of MHC molecules expressed by an individual?

Answer 26

Polymorphism and polygeny

Question 27

What 3 important things does MHC complex control?

Answer 27

1. MHC recognition–>T cell recognition of antigen
2. Immune response (Ir) genes (selectively respond to antigen)
3. Graft rejection (reject organ grafts)

Question 28

Explain MHC restriction

Answer 28

T cell recognition can only happen if the correct MHC allele & antigen are bound
-if 1 of them is incorrect there is no recognition

Question 29

Syngeneic

Answer 29

Genetically identical due to inbreeding
-No polymorphism
-same MHC alleles/haplotype

Question 30

Allogenic

Answer 30

Genetically disparate (wild mice)
-different MHC alleles/haplotypes

Question 31

Congenic

Answer 31

Genetically identical w/ exception of 1 genetic locus
-made by backcrossing & selection
-congenic mice are homozygous for a and b haplotype

Question 32

True or false: Immune response (Ir) genes map to the MHC

Answer 32

True

Question 33

True or false: MHC peptide binding is promiscuous (one type of peptide) NOT highly specific

Answer 33

True

Question 34

How does graft rejection work?

Answer 34

-T cells that recognize self antigens (MHCs) with high affinity are eliminated through the process of negative selection graft is ACCEPTED
-T cells that are non self (foreign) are NOT deleted graft is REJECTED–>T lymphocytes use cytotoxic T cells to kill skin cells

Question 35

T cell receptors structurally resemble?

Answer 35

Fab of immunoglobulins