T cell Immunity

Question 1

Anergy

Answer 1

state of nonresponsiveness to antigen; can’t respond under optimal conditions of stimulation

Question 2

APC

Answer 2

specialized cells that present antigen and display their peptide fragments on the cell surface together with other costimulatory proteins required for activating naive T cells

Question 3

what are the major APCs that activate naive T cells?

Answer 3

dendrites, macrophages, and B cells

Question 4

B7 molecules

Answer 4

major T cell co-stimulatory molecules, B7.1 and B7.2. Closely related and both bind CD28

Question 5

how many B7 molecules are there? what expresses them?

Answer 5

2; APC

Question 6

What is another name for the B7 molecules?

Answer 6

B7.1=CD80, B7.2=CD86

Question 7

CD28

Answer 7

receptor on T cells for the B7 costimulatory molecules

Question 8

why is Cd28 important?

Answer 8

plays a huge role in activation and proliferation of T cells after they first encounter an antigen

Question 9

Why is CTLA-4 important?

Answer 9

high affininity receptor for B7 molecules on T cells; plays a critical role in shutting of the T cell response

Question 10

Granzymes

Answer 10

serine proteases that are involved in inducing apoptosis in the target cells

Question 11

Homeostatis

Answer 11

state of physiological normality; in case of immune system

Question 12

What does homeostatsis mean in the immune system

Answer 12

its state when the person is unaffected (ie numbers of lymphocytes)

Question 13

IL-2 is

it functions to

Answer 13

cytokine produced by activated naive T cells; promote further differentiation and proliferation

Question 14

why is IL-2 important?

Answer 14

key cytokine in development and contraction of the an adaptive immune response

Question 15

IL-7 is

it functions to:

Answer 15

hematopoietic growth factor secreted by stromal cells in the bone marrow and thymus and other cells

promote T cell development, survival, and homeostasis

Question 16

Perforin

Answer 16

protein that can polymerize to form membrane pores that are an important part of the killing mechanism in cell-mediated cytotoxicity

Question 17

Other than stromal cells in the bone marrow and thymus, what other cells secrete IL-7

Answer 17

keratinocytes, dendritic cells, hepatocytes, neurons, and epithelial cells

Question 18

what is a naive T cell?

Answer 18

Naive T cells have not yet encountered their antigen

Question 19

What are the signals needed to maintain T cell homeostatis?

Answer 19

TCR: pMHC interaction

IL-7

Question 20

What are the steps for T cells encountering their antigen?

Answer 20

1. T cells enter a lymph node across a high endothelial venule in the cortex
2. T cells monitor antigen presented by macrophages and dendritic cells
3. Cells that do not encounter specific antigen leave by efferent lymph
4. T cells that encounter their specific antigen proliferate and differentiate into effector cells

Question 21

What are the functions of the accessory molecules?

Answer 21

control routes of T migrations, strengthen adhesion with APCs, signal transduction

Question 22

how is control of cell migration routes maintained?

Answer 22

selectins, integrins, and chemokine receptors control migration in and out of lymph nodes

control release of effector and memory T cells to site of infection

Question 23

How is the adhesion with APC’s strengthed?

Answer 23

integrins;

Question 24

How is affinity of integrins increased?

Answer 24

affinity of integrins is increased by cytokines produced during inflammation and Ag recognition

Question 25

What molecules facilitate transduction and how?

Answer 25

CD4 and CD8 coreceptors recognize MHC molecules CD28-CD40L are receptors for costimulators expressed on APCs

Question 26

What is the role of the interaction between ICAM-1 and LFA-1

Answer 26

prolongs cell to cell contact between the APC and T cell, as they must be bound for 6-12 hours to activate the naive T cell

Question 27

Describe the process of the T cells and APCs

Answer 27

1.T cell binds APC through LFA1:ICAM1, acts as tether 2.subsequent binding of T cell receptor signals LFA1 3. LFA1 undergoes a conformational change that increases the affinity for ICAM1 allows for a stronger interaction between APC and T cell

Question 28

What are the 2 signals required for activating naive T cells?

Answer 28

signal 1: antigen recognition | signal 2: microbes or substances released during innate immune response to microbes

Question 29

Why do you need signal 1 (antigen recognition)?

Answer 29

ensures that the response is antigen specific

Question 30

Why do you need signal 2? what does it mean?

Answer 30

ensures that the immune system is responding to microbes and not to harmless antigenic substances activated APCs express molecules which in turn bind their respective ligands on T cells to deliver a costimulatory signal.