Immunology - T-Cells

Front 1

What are the 2 central roles of T cells in immunity?

Back 1

Secrete cytokines (CD4+)
Inducing osmotic lysis (CD8+)

Front 2

Where does somatic recombination of the TCRs occur?

Back 2

Thymus

Front 3

When can TCRs recognize antigen fragments?

Back 3

Only when they are expressed by either class I or class II MHC
CD8+=class I
CD4+=class II

Front 4

What are the 2 transmembrane polypeptide chains of TCRs?

Back 4

Alpha/beta
Gamma/delta

Front 5

Which of the 2 polypeptides comprise the majority of TCRs?

Back 5

Alpha/beta 90%

Front 6

What does each heterodimeric TCR express on the cell surface?

Back 6

5 invariant polypeptides= CD3

Front 7

What is the purpose of CD3?

Back 7

Link the antigen binding receptor of the T cell with signaling pathways

Front 8

What is the TCRalpha composed of?What is the TCRbeta composed of?

Back 8

alpha = V and J segment (VJ)
beta = V D J segments

Front 9

What is meant by the term T-cell repertoire?

Back 9

Because of somatic recombination 10 to the 12 – 10 to the 15 different TCRs can potentially give rise to a unique T-cell clone and as many as 25,000 TCRs on any cell, collectively they make up the repertoire

Front 10

Which TCR undergoes somatic recombination first?

Back 10

TCR beta

Front 11

What is the diversity in the T-cell repertoire the result of?

Back 11

1. Multiple copies of germline V, D, J segments
2. Random selection and combination of VDJ
3. Junctional diversity generated by addition or deletion of bases
4. Random assortment of TCRalpha and TCRbeta chains

Front 12

What leads to the generation of T cells expressing TCRs that may be autoreactive?

Back 12

Random selection

Front 13

Progenitor cells originating in the bone marrow differentiate to naïve mature T cells under the influence of the thymic microevironment secreting which cytokine?

Back 13

IL-7

Front 14

What are the characteristics of phase 1 of development phases of TCR?

Back 14

Somatic recombination of TCRbeta
Expression of pre-TCR

Front 15

What is the pre-TCR composed of?

Back 15

TCRbeta polypeptide linked to invariant polypeptide chain= preTalpha that associates with CD3

Front 16

What is expressed on the cell surface during phase I? what is its purpose?

Back 16

CD2
Serves as T-specific marker

Front 17

What stage is referred to as negative selection?Where does this occur?

Back 17

Phase IV
Thymic cortex or medulla

Front 18

What do naïve lymphocytes travel in when they leave the blood into lymph nodes?

Back 18

High endothelial venules (HEV)

Front 19

What does extravasation of naïve lymphocytes into tissues at HEV require?

Back 19

1. Interaction of L-selectin on lymphocytes with its ligand on endothelial cells to induce lymphocytes rolling

2. Activation of integrins (LFA-1) increasing adhesiveness

3. Lymphocyte secretion of matrix metalloproteinases that proteolytically degrade collagen to generate channels in subendothelial basement membrane

4. Transendothelial migration of lymphocytes into tissue

Front 20

primary encounter w/ antigen occurs where?

Back 20

secondary lymphoid tissue (any secondary lymphoid tissue)

Front 21

How are B and T cells in secondary tissue arranged?

Back 21

B cells in follicles, T cells surrounding follicles

Front 22

What part of follicle are naive B cells activated?

Back 22

Outer part of follicle (T cell help is not limiting here)

Front 23

What are germinal centers associated with?

Back 23

1. B cell clonal expansion,
2. isotype switching,
3. affinity maturation,
4. differentiation to plasma cells, memory cells.

Front 24

What is the essential signal for formation of germinal centers and B cell activation?

Back 24

Interaction between CD40/CD40L between T cells and B cells.

Front 25

How long after immunization do B cells differentiate to plasma cells?

Back 25

4 days

Front 26

T independent antigens usually give which Ig?

Back 26

IgM

Front 27

During primary immune response, which is found in higher concentration, IgM or IgG?

Back 27

IgM

Front 28

During secondary immune response, which is found in higher concentration, IgM or IgG?

Back 28

IgG

Front 29

Why do B cells enter lymph nodes via afferent lympahtics and not HEVs?

Back 29

B cells have reduced expression of L selectin

Front 30

What infantile hypogammaglobulinemia caused by?

Back 30

Absence or severe reduction of B cells

Front 31

Patients with hypogammaglobulinemia present how?

Back 31

Chronic severe bacterial infections

Front 32

What do patients w/Hyper Igm syndrome present on a molecular basis?

Back 32

Lack of CD40 / CD40L

Front 33

How do patients w/Hyper IgM syndrome present?

Back 33

Defective isotype switching

Front 34

What is the network theory of immune regulation?

Back 34

sIg complementary to Fab (i.e. look like antigen) mimic antigen for later Ig formation

Front 35

How long do B memory cells survive?

Back 35

Weeks or months (they are not in cell cycle)

Front 36

Why are dendritic cells the most effective Antigen Presenting cell?

Back 36

Co-stimulatory molecules (CD80/B-7) are always found on their surface, whereas co-stimulatory molecules are induced on other APCs (ie. macrophages and b-cells)

Front 37

What is the importance CD28 on T-cells?

Back 37

CD28 triggers a signal transduction to stabilize mRNA for IL-2.

IL-2 = growth factor for T-cells