Cell Mediated Immunity

Question 1

What is cell mediated immunity

Answer 1

Immune response to intracellular pathogens

Question 2

Cells involved in cell mediated immunity

Answer 2

• Antigen-specific (T helper-CD4 and T cytotoxic-CD8)

* Antigen-non-specific (NK cells, macrophages, neutrophils, and eosinophils)

Question 3

Functions of cell mediated immunity

Answer 3

• Activation of M1 macrophages

* Induce B cells (IFN-g) to class switch (IgG) to opsonize • Direct killing (Tc)

Question 4

Triggers of cell-mediated immunity

Answer 4

A) Phagocytosed microbes
(exogenous microbes)

B) Cytosolic microbes

Question 5

What do naive T lymphocytes recognize

Answer 5

Antigen presented by dendritic cells

Question 6

Antigen recognition and co -stimulation

Answer 6

Signal 1- foreign

Signal 2 - Danger

Question 7

Signal 1 - Foreign

Answer 7

▪ TCR recognizes peptide on APC

▪ CD4 or CD8 coreceptors recognize the MHC molecule ▪ Co-receptor engage

Question 8

Signal 2 :Danger

Answer 8

T cell activation are triggered by co-stimulator proteins

▪ Adhesion molecules strengthen the binding of T cells to APCs

Question 9

CD28

Answer 9

• Co stimulation
• B7-1/B7-2
• APCs

Question 10

CTLA-4

Answer 10

• inhibition
• B7-1/B7-2
• APCs

Question 11

PD-1

Answer 11

-inhibition
-PD-L1/PD-L2
APCs and tumor cells

Question 12

LFA-1

Answer 12

• adhesion and signal transduction
• ICAM1
• APCs ,endothelium

Question 13

What is TCR associated with

Answer 13

CD3

Question 14

Polyclonal activators (Non-specific):

Answer 14

Antibodies for the TCR or CD3
• Carbohydrate-binding proteins (e.g.,
phytohemagglutinin) • Superantigens

Question 15

• Superantigens

Answer 15

Cause pathology through massive load of cytokines (toxic shock syndrome)
✓T cell mitogens: induce cell proliferation

Question 16

CAMs

Answer 16

• Selectins, mucins, integrins, and immunoglobulin superfamily
• Function: Stabilization of binding between ligand on APCs and T-cells
• Overcome moderate affinity between TCR and peptide/MHC

Question 17

CD40 ligand (CD40L or CD154)

Answer 17

they activate APCs to express more B7 co- stimulators and to secrete cytokines (e.g., IL-12) to enhance T cell differentiation

Question 18

▪ Proteins homologous to CD28:

Answer 18

CTLA-4 (CD152) or PD- 1 are involved in terminating the immune response

Question 19

Agents that block B7:CD28

Answer 19

treatment of rheumatoid arthritis, graft rejection etc

Question 20

Antibodies that block CTLA-4 or PD-1

Answer 20

enhance immune response in cancer patients

Question 21

What is the first cytokine produced by CD4+ T cells

Answer 21

IL2

1-2 hours after activation

Question 22

Secretion of Cytokines and expression of cytokine receptors assists with

Answer 22

Autocrine signal

• survival, proliferation and differentiation

Question 23

What defect is found in SCID

Answer 23

Defect in common gamma chain

Question 24

What activates macrophages (M1) in CMI

Answer 24

IFN or IFN gamma

Question 25

Functions of M1 macrophages

Answer 25

- pro inflammatory - microbicidal - Tumorcidal - Th1 response - APC - killing intracellular pathogens

Question 26

M2 macrophage

Answer 26

Activated by IL4,13 and 10 as well as TGF-b - anti inflammatory - parasites - Tumor promotion - Th2 response

Question 27

The primary events in Cytotixic T Lymphocytes -mediated death are

Answer 27

▪ Conjugated formation ▪ Membrane attack ▪ CTL dissociation ▪ Target cell destruction

Question 28

Conjugate formation

Answer 28

▪Cell adhesion (LFA-1 on CTL binds ICAM on target cell) | ▪Recognition of MHC I: Ag on target cell

Question 29

Membrane Attack

Answer 29

``` ▪ Granules in CTLs • Perforin • Granzymes ▪ Exocytosis of granule contents • Perforin action similar to C9 • Granzymes act as nucleases ```

Question 30

CTL mechanisms of killing

Answer 30

Fas/FasL - the combo binds to FADD - activates procaspase 8 and caspase 8 - cascade - cell death

Question 31

NK cells -

Answer 31

- defend against viruses, other intracellular pathogens and tumors - not MHC restricted - no memory - no TCR/CD3 - recognizes glycolipid no CD1d

Question 32

What determines activation of NK cells

Answer 32

balance between activating and inhibitory receptors

Question 33

What and when do NK CELLS do their job

Answer 33

Recognize altered cell surface molecules (lowered Class I MHC) ▪ Back-up plan when T cytotoxic cells cannot destroy viral infected cells or tumor cells (No MHCI

Question 34

Functions of NK cells

Answer 34

A. Cytotoxic granule mediated cell apoptosis (perforin, granzymes, a-defensins) B. Induce infected macrophages to kill : Respond to IL-12 with IFN-g production C. Antibody-dependent cell mediated toxicity