Defense Against Infection: Adaptive Immunity

Question 1

one of the important byproducts of the innate immune response is the facilitation of what?

Answer 1

facilitation of antigen-processing and presentation that occurs in the secondary lymphoid tissues, giving rise to the adaptive immune response

Question 2

the inflammatory responses produced during the early innate phase of immune responses does what? How does this help adaptive immunity?

Answer 2

increases the flow (via the lymph) of antigen and APCs (that have taken up antigen) from inflammatory sites into the draining secondary lymphoid tissue;

adaptive immune responses can now be initiated in these secondary lymphoid tissues

Question 3

3rd phase of response to infection which occurs when?

Answer 3

> 96 hours post-infection

Question 4

When is initiation of adaptive immune responses is triggered?

Question 5

adaptive immune responses require several days to develop. What is happening during this time?

Question 6

1st step in Development of Adaptive Immune Responses?

Question 7

Give the steps of the activation of antigen-specific T cells in the secondary lymphoid tissues

Answer 7

• immature dendritic cells in the tissues take up antigen,
• stimulated by infection to migrate (via the lymphatics) to draining lymph nodes where they can present antigen to naïve T cells

Question 8

antigens introduced directly into the blood are taken up primarily by what? activation of antigen-specific T cells occurs where?

Answer 8

by antigen-presenting cells in the spleen,

in the white pulp of the spleen

Question 9

the trapping of antigen by APCs that migrate to lymphoid tissues assures a high rate of MHC:peptide complex sampling by naïve T cells; this is critical because of what reason?

Answer 9

T cells must sample a given MHC:peptide complex before specific recognition of the peptide occurs;

high contact rate between T cells and APCs is required for efficient sampling to occur

Question 10

Describe the path from antigens in the gut to presentation to T cells

Answer 10

antigens in the gut are delivered from the lumen into Peyer’s patches (and other 2 ̊ lymphoid tissues) by M cells;

these antigens are processed and presented by APCs to T cells

Question 11

Why are M cells vulnerable to infection?

Answer 11

M cells do not produce mucous and they do not have a thick protective glycocalyx.

So any antigen is immediately delivered straight into secondary lymphoid tissues to be presented to naive T cells by APCs

Question 12

when a naïve T cell encounters specific peptide bound to MHC, the interaction between the T cell and the dendritic cell tightens (via adhesion molecules). What does is the result?

Answer 12

T cell is stimulated to proliferate and differentiate, resulting in the production of armed antigen-specific effector T cells

Question 13

effector CD8+ cells (CTLs) are programmed to kill cells in what way? What will target a cell for this fate?

Answer 13

an antigen-specific manner

any cell that presents (on its surface) the CTL’s cognate peptide antigen bound to MHC class I molecules will be killed

Question 14

CD4+ cells differentiate into two different types of effector cells dependent on what?

Answer 14

T helper 1 CD4+ cells (TH1 cells) or T helper 2 CD4+ cells (TH2 cells)

specific cytokines

Question 15

How is it decided whether a T helper cell will be a TH1 or TH2 cell?

Answer 15

• Naïve CD8+ cells emerging from the thymus are destined to become CTL
• CD4+ cells, however, are undecided when they leave the thymus;

all CD4+ cells that leave the
thymus are considered TH0 cells;

the decision to become a TH1 or a TH2 cell is made upon 1st encounter with antigen;