Effector T lympocytes

Question 1

Define Naive T cell?

Answer 1

Mature recirculating T cells that have not yet encountered antigen

Question 2

Define Effector T Cells?

Answer 2

Encountered antigen, Proliferated and differentiated into cells that participate in host defence

Question 3

Define Memory T cells?

Answer 3

Encountered Antigen, contracted, ready to respond to future infections

Question 4

Define Target cells?

Answer 4

Cells on which effector T cells act.

Question 5

When is T cell mediated immunity required?

Answer 5

When pathogens are intracellular- hidden in the cell (TB,Malaria,HIV ect) When organisms evolve to escape antibody recognition- either by changing shape (influenza) or by coating antigen in carbohydrate (HIV) or producing decoy antigens (RSV) Sometimes antibody is insufficient

Question 6

Why are APC’s important in the induction of T lymphocyte responses?

Answer 6

T cells are only activated by fragments of antigens (peptides) presented in the context of MHC molecules

Question 7

Where do dendritic cells mature and present antigen on mhc?

Answer 7

lymph node

Question 8

Lympocytes recirculate from……. and ……. to ……….. ………

Answer 8

Lymphocytes recirculate from blood and lymph to lymphoid organs.

Question 9

Summarise the effector functions of CD8 + effector T cells?

Answer 9

CD8+ effector T cells destroy target cells such as virus infected cells or tumours Recognise MHCI: Peptide Complexes Effector CTLs secrete granules

Question 10

Summarise the effector function of Cytotoxic T cells?

Answer 10

CTLs kill their targets by apoptosis

Question 11

What do CTLS store in their granules?

Answer 11

Perforin and granzymes

Question 12

What is the function of perforin?

Answer 12

Perforin molecules polymerise and form poers in the target cell membrane

Question 13

What is the function of granzymes?

Answer 13

They induce programmed cell death in the target cell, thus eliminating cells that have become cancerous or are infected with viruses or bacteria.

Question 14

What happens after CTLs recognise infected targets?

Answer 14

granules are released

Question 15

Summarise the effector function of T lymphocytes including cell-mediated cytotoxicity

Answer 15

• Cytotoxic T cells (CTL) kill their targets by programmed cell death = apoptosis • Apoptosis is characterized by fragmentation of nuclear DNA • CTL store perforin, granzymes, granulysin in cytotoxic granules • granules are released after target recognition • perforin molecules polymerise, form pores • FasL (on CD8) can induce cell death by interacting with Fas on target cells

Question 16

What does Fas-FasL interaction induce?

Answer 16

apoptosis

Question 17

What type of cell activates Macrophages to promote killing of intracellular pathogens?

Answer 17

CD4+ Th1 effector cells

Question 18

What does Th1 stand for?

Answer 18

T helper 1 cells

Question 19

T helpers are defined by the cytokines they produce and the transcription factors they use True or false

Answer 19

True

Question 20

What does Th1 cells boost?

Answer 20

Boost intracellular immune response

Question 21

What does TH1 produce?

Answer 21

Produce interferon gamma

Question 22

What do activated macrophages express and release?

Answer 22

They express increased levels of CD40 and TNF-alpha receptors Secrete TNF-alpha

Question 23

Activated macrophages express increased levels of CD40 and TNF-a receptors, and secrete ……. which synergises with …….. in the induction of antimicrobial effector mechanisms.

Answer 23

TNF-alpha and IFN-gamma

Question 24

What is the primary role of delayed type hypersensitivity?

Answer 24

primary role in defence against intracellular pathogens

Question 25

What induces DTH?

Answer 25

Intracellular parasites Intracellular bacteria Intracellular fungi Intracellular Viruses (herpes)

Question 26

What does the DTH produce if the antigen is not a microbe, like in contact hypersensitivity?

Answer 26

the DTH produces tissue injury without protection = “hypersensitivity”

Question 27

How long, after antigen exposure, does local swelling with cellular infiltrates occur?

Answer 27

24-72 hours

Question 28

What happens if the source of antigen is not eradicated in DTH?

Answer 28

Chronic stimulation, granuloma formation

Question 29

What type of cells are involved in DHC?

Answer 29

Th2 and Th1 cells

Question 30

What do Th1 cells release in DHC?

Answer 30

Chemokines Cytokines (IFN-gamma) Cytotoxins Release inflammatory cytokines that affect blood vessels (TNF-beta)

Question 31

Name 2 pathological reactions caused by T cells?

Answer 31

Autoimmunity - antigenic peptide derived from self protein Rejection (transplants) - antigenic peptide derived from self protein of transplant donor

Question 32

What is the function of CD4+ Th1 effector cells?

Answer 32

Activate infected macrophages which present peptides in context with MHC class II molecules on their cell surface. Activate CD8 T cells

Question 33

What is the function of CD4+ Th2 effector cells?

Answer 33

They are also MHC class II restricted and help B cells differentiate into antibody secreting plasma cells. Boost anti-multicellular organism response

Question 34

What is the function of Th17 cells?

Answer 34

produce a particular set of inflammatory cytokines They are also protective against some bacterial infections and also mediate pathogenic responses in autoimmune diseases

Question 35

What is the function of Regulatory T-cells (Treg) cells?

Answer 35

Inhibit the activation of of naive and effector T cells by contact dependant mechanism or by secreted cytokines T cells that regulate the activation or effector functions of other T cells natural and induced regulatory T cells necessary to maintain tolerance to self antigens The regulatory T cells (Tregs /ˈtiːrɛɡ/), formerly known as suppressor T cells, are a subpopulation of T cells that modulate the immune system, maintain tolerance to self-antigens, and prevent autoimmune disease. Tregs are immunosuppressive and generally suppress or downregulate induction and proliferation of effector T cells.[1]

Question 36

When are effector T cells activated?

Answer 36

Helper T cells become activated when they are presented with peptide antigens by MHC class II molecules, which are expressed on the surface of antigen-presenting cells (APCs). Once activated, they divide rapidly and secrete small proteins called cytokines that regulate or assist in the active immune response.