module 07 section 01 (effector cells in CMI)

Question 1

define effector cells

Answer 1

cells that have a biological effect rather than a regulating function

Question 2

which type of cell is responsible for the immune response in cell-mediated immunity?

Answer 2

effector cells

Question 3

the cell-mediated immune response can be divided into two phases based on what?

Answer 3

the type of effector cells present

Question 4

what are the two phases of cell-mediated immunity

Answer 4

nonspecific and specific

Question 5

what are the cells involved in the nonspecific response?

Answer 5

macrophages and NK cells

Question 6

what is the primary result of the nonspecific response?

Answer 6

increased IFN-a and IFN-B

Question 7

what is the later result of the nonspecific response?

Answer 7

continued contribution of macrophages will activate Th1 cells

Question 8

when does the nonspecific response occur (how many days after viral infection)?

Answer 8

0-5 days after infection

Question 9

what are the cells involved in the specific response?

Answer 9

cytotoxic T-cells

Question 10

what are cytotoxic T-cells activated by for the specific response?

Answer 10

Th1 cells

Question 11

when does the specific response occur (how many days after viral infection)?

Answer 11

5-12… days after infection

Question 12

the effector cells of cell-mediated immunity carry out their responses in two ways, what are they?

Answer 12

antigen-nonspecific and antigen-specific

Question 13

define the antigen-nonspecific response

Answer 13

• macrophages, NK cells
• these cells can recognize pathogens, but are not specific to a particular antigen (I.e. they do not distinguish one pathogen from another)

Question 14

define the antigen-specific response

Answer 14

• Th1 cells and cytotoxic T-cells
• these cells are specific for a processed pathogen antigen in complex with MHC class I
• *Th1 does not have direct cytotoxic activity - activates cytotoxic T-cells

Question 15

we know that the initial macrophage response is nonspecific, does this change during later stages?

Answer 15

yes - antigen-specific Th1 cells play a role in activating the macrophage response

Question 16

list 4 characteristics of the macrophage response

Answer 16

(1) they produce ROI, NO and lysosomal enzymes
(2) they secrete cytokines
(3) they increase the ecpression of B7 costimulators and MHC molecules
(4) they play a role in the activation of NK cells during infection

Question 17

the NK cell response can be activated by which factors?

Answer 17

IFN-a, IFN-B and IL-2

Question 18

list 4 characteristics of the Nk cell response

Answer 18

(1) these are large granualr lymphocyte-like cells that lack antigen-specific receptors
(2) they’re capable of Fas-mediated killing
(3) they control infection during the period required for generation of specific cell-mediated effector cells
(4) they’re involved in antibody-dependent cell-mediated cytotoxicity

Question 19

list common pathogens presented by macrophages to Th1 cells

Answer 19

mycobacterium tuberculosis, mycobacterium leprae, leishmania donovani, pneumocystis carinii

Question 20

CD4+ Th1 cells interact with which cell? where is the pathogen?

Answer 20

macrophages - pathogen is engulfed by macrophage and stored in vesicles, then presented to Th1 via MHC class II complex on the macrophage

Question 21

list common pathogens presented by virally infected cells to cytotoxic T-cells

Answer 21

vaccinia virus, influenza virus, lyssavirus (rabies), listeria monocytogenes

Question 22

CD8+ cytotoxic T-cells interact with which cell? where is the pathogen?

Answer 22

target cell - pathogen is in the cytosol of the virus-infected cell, then presented to cytotoxic T-cell via MHC class I complex on the virus-infected cell

Question 23

what is delayed-type hypersensitivity?

Answer 23

type IV hypersensitivity response mediated by sensitized helper T-cells (due to the release of various cytokines)

Question 24

what are the physiological roles of delayed-type hypersensitivity?

Answer 24

macrophage clearance, killing of intracellular pathogens (such as mycobacterium tuberculosis), etc.

Question 25

ultimately, delayed-type hypersensitivity is:

Answer 25

the result of cytokine release from cell-mediated immunity effector cells

Question 26

what is delayed-type hypersensitivity associated with?

Answer 26

tissue damage

Question 27

is delayed-type hypersensitivity deleterious to the host due to the associated tissue damage? why or why not?

Answer 27

not necessarily - it can result in containment of intracellular pathogens that would otherwise cause severe disease

Question 28

delayed-type hypersensitivity responses in the skin have been used to test what?

Answer 28

cell-mediated immunity in vivo

-i.e. antigen (e.g. M. tuberculosis) introduced intradermally

Question 29

a positive TB test response requires a subjects exposure to the antigen to be at least _____ prior to skin testing?

Answer 29

4-6 weeks

Question 30

when/what is a positive TB test marked by?

Answer 30

• erythema and induration (increase in the fibrous texture of tissue - commonly associated with inflammation and marked by loss of elasticity)
• usually 10 mm (indicates immune sensitization only)
• 48-72 hours post injection

Question 31

explain the role of cytokines (3)

Answer 31

• they modulate the expression of cell adhesion molecules on the endothelial cells of the local vessels
• they recruit blood-derived monocytes
• they can also promote monoycyte to macrophage differentiation in the tissue, macrophage phagocytosis and bacterial killing

Question 32

provide an overview of cytokines in action

Answer 32

• Th1 effector cell from a previous immunization (memory) recognizes the antigen and releases cytokines, which act on the vascular endothelium
• results in the recruitment and activation of more T-cells, neutrophils and macrophages to the site of anitgen injection
• recruited cells cause inflammation to the area (commonly seen as an induration in TB testing)