one of the important byproducts of the innate immune response is the facilitation of what?
facilitation of antigen-processing and presentation that occurs in the secondary lymphoid tissues, giving rise to the adaptive immune response
the inflammatory responses produced during the early innate phase of immune responses does what? How does this help adaptive immunity?
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
3rd phase of response to infection which occurs when?
> 96 hours post-infection
When is initiation of adaptive immune responses is triggered?
adaptive immune responses require several days to develop. What is happening during this time?
1st step in Development of Adaptive Immune Responses?
Give the steps of the activation of antigen-specific T cells in the secondary lymphoid tissues
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
antigens introduced directly into the blood are taken up primarily by what? activation of antigen-specific T cells occurs where?
by antigen-presenting cells in the spleen,
in the white pulp of the spleen
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?
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
Describe the path from antigens in the gut to presentation to T cells
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
Why are M cells vulnerable to infection?
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
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?
T cell is stimulated to proliferate and differentiate, resulting in the production of armed antigen-specific effector T cells
effector CD8+ cells (CTLs) are programmed to kill cells in what way? What will target a cell for this fate?
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
CD4+ cells differentiate into two different types of effector cells dependent on what?
T helper 1 CD4+ cells (TH1 cells) or T helper 2 CD4+ cells (TH2 cells)
How is it decided whether a T helper cell will be a TH1 or TH2 cell?
• 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;