MIIM - Ocular Defences: The Immune System III - Week 4 Flashcards
Is the MHC marker and peptide recognition by a T cell alone enough to activate it?
No
Which cell is the best antigen presenting cell?
Dendritic cell
In non-inflamed tissue, how efficient are dendritic cells at capturing antigens and stimulating naïve T cells?
Highly efficient at capturing antigens but poor stimulators of naïve T cells.
Do dendritic cells have a high or low level of MHCII on their plasma membrane?
Low
What is secreted by dendritic cells?
TGF-β
Can dendritic cells migrate easily to lymph nodes?
No, its restricted
What initiates dendritic cell maturation, and what is it essential for?
Initiated when it binds pathogens.
Essential for naïve T cell activation.
Name 6 maturation events for dendritic cells.
Migration of the cell to draining lymphoid tissue
Increased antigen processing
Increased MHCI and MHCII expression
Increased surface espression of adhesin
Expression of co-stimulatory molecules
Secretion of cytokines
Do maturing dendritic cells gain or lose capacity to capture antigens?
Lose
Name the three molcules involved in the best characterised co-stimulatory signal.
CD80 and CD86 on the surface of the APC, and CD28 which is found on all T cells.
Define signal 1.
The antigen specific recognition by a T cell
Define signal 2.
A co-stimulatory signal needed in addition to signal 1, given by mature dendritic cells.
Define signal 3.
Secretion of selected cytokines by the mature antigen presenting cell that has successfully activated and costimulated a naïve T cell.
Once a naïve CD4 T cell receives signals 1 and 2, what does it express (2) and secrete? What else?
It expresses CD40L and IL-2R.
It secretes IL-2 and now proliferates.
What happens to a CD4 T cell with signal 3?
It differentiates, and performs its effector function.
What does signal 3 facilitate in CD4 T cells?
Facilitates differentiation along several possible pathways, each leading to a cell with a particular function.
Where do mature APCs interact with CD8 T cells?
Secondary lymphoid tissue
If a B cell binds an antigen in the lymphoid tissue, can it both release antibodies as well as act as an APC?
Yes
When a B cell act as an APC, which MHC marker does the antigen end up on?
Class II
What do activated T cells expressing CD40L do with it? What happens after this (4)? What kind of cell additionally arises from this?
It binds B cells that display CD40 and antigen peptides on their MHC.
The B cells proliferate, isotype switch, and undergo affinity maturation, and secrete their antibodies.
Some of these B cells differentiate into memory B cells.
Are CD80 and CD86 constitutively expressed on APCs? What about CD40L on T cells?
No, none of them are constitutively expressed (only weakly expressed).
Define PAMP.
Pathogen associated molecular pattern
What interaction is a major signal to induce expression of CD80 and CD86?
Their interaction with PAMPs
Can T cells become activated in the absence of co-stimulation?
No
Can T cells express CD40L if they are not activated?
No
Can B cells be fully activated in the absence of CD40 ligation by CD40L?
No
Once CD4 T cells are activated and migrated to the infection site, what two things do they do there?
Activate tissue macrophages
Activate other cell types such as fibroblasts, neutrophils, and keratinocytes.
What molecule do cytotoxic T cells use to kill infected cells?
Perforin
Name three ways T cell activation can be inhibited, and give one example for each.
Immunosuppressive drugs - inhibiting IL-2 production
Antibodies - block T and APC/T and B cell interactions
Soluble ligands - block co-stimulatory interactions
Describe briefly how the innate and adaptive immune systems activate each other (5).
Innate activates adaptive by increasing co-stimulation via APC action and producing cytokines inducing T cell differentiation.
Adaptive activates innate by producing antibodies that act as opsonins triggering phagocytosis and complement cascades, and producing cytokines recruiting macrophages and other phagocytes.
Name the cytokine responsible for upregulating the production of the following antibodies:
IgA
IgG
IgE
IgA - TGFβ
IgG - IFNγ
IgE - IL-4
