Midterm 2 flash cards
What are the methods of control of the immune system
-cytokines signaling proteins amplifying/supressing
-Tolerance so immune system dosent attack itself
-Regulatory (tregs) which are peackeers preventing overreation
-Activation/Apoptosis balance
Ways that the immune system are shut off
Indirectly:less antigen present to stimulate an immune response so DCs die after a few days
Directly:Apoptosis and by molecular inhibition of immune functions (activated T cells are inherently pro apoptotic
Molecular examples of Direct immune response
Tim-3:A receptor on T cells that inhibits their activation and promotes cell death
PD1/ PD1L: PD-1 on T cells binds to PD-L1 to suppress immune responses, helping tumors evade detection
CTLA-4:receptor competes with CD28 to inhibit T cell activation, promoting immune tolerance.
IL-2 is for what?
-Produced by T cells and is the main growth factor for T cells.
-When T cell activated, they produce IL-2 leading to cell division and immune cell expansion.
IL-4 is for what?
-made by macrophages and Th2 cells
-Help naïve Th cells (immature T helper cells) develop into Th2 cells.
-Stimulate the immune system to produce antibodies.
IL-5
produced by Th2 cells and it functions to promote the growth and
differentiation of B cells and eosinophils. It also activates mature eosinophils.
TGF-β
It inhibits the proliferation of T cells and the activation of macrophages
INF-γ
What are the different pathogens each adaptive system is more geared to?
Th1: viral/bacterial attacks in the blood and tissue
Th2: mucosal/parasitic infections.
central tolerance says that
-B and T cells must:
not react to self antigens
-Be restricted to self MHC molecules (T cells), so they will only react to presented antigens
Where is cell selection done
epithelial cells in the cortex
positive selection is when?
Cells that recognize MHC-peptide
complexes receive rescue signals that
Prevent apoptosis.
What happens to CD4 and CD8 T cells that survive MHC
migrate to the medulla of the thymus where they are
Tested for response to self antigens
Negative selection is a process that happens in… and prevent…
Negative selection is a process that happens in the thymus to prevent T cells from attacking the body’s own tissues.
explain how negative selection happens:
1)Thymic dendritic cells show T cells samples of self-peptides using MHC molecules.
2)The AIRE gene helps thymic cells produce proteins from various organs, even though those proteins are normally only found in specific parts of the body. This gives T cells a wide view of what “self” looks like.
3)The dendritic cells essentially present a “snapshot” of self-proteins from around the body to the developing T cells.
4)If a T cell binds too strongly to these self-peptides presented by MHC, it is seen as a threat because it might attack the body’s own cells. As a result, the T cell is deleted (undergoes apoptosis), preventing autoimmunity.
explain tregs:
Regulatory T cells (Tregs) are made in the thymus as part of the immune system’s self-regulation process.
Some CD4 T cells that have a slightly stronger reaction to the body’s own proteins (self-antigens) during negative selection are turned into natural Tregs (nTreg) instead of being eliminated.
About 5% of the CD4 T cells circulating in your body are these natural Tregs.
Unlike helper T cells, which activate the immune response, Tregs suppress or “turn down” the immune response to prevent it from attacking the body’s own cells.
In addition to natural Tregs, inducible (adaptive) Tregs can develop later in response to inflammation, and they can help regulate the immune response to both self and foreign antigens after an immune reaction.
what does maintaining peripheral tolerance mean
prevent the immune system from attacking the body’s own tissues.
What do treg cells produce that help calm the immune system down
anti-inflammatory cytokines like IL-10 and TGF-β
Name two main things treg cells do
-regulate activation of other T cells
-maintain peripheral tolerance to self antigens
-Produce cytokines that shut down the immune system
What tests do B cells undergo
1) postitive selection: make sure BCR receptors are working
2) Negative selection: make sure cells dont react to self.
Difference between B and T cell growth in terms of which is easier to make
60 mil T cells are made & ONLY 2 million make it
meanwhile
30-40% B cells survive
What does compartmentalization mean
Naive t cells don’t get exposed to everything that could trigger an immune response. becuase they are floating around the body and the chance for them to meet one is lower than if it was in the lymph nodes.
What is co-stimulation
When T cells encounter antigens outside the thymus binds to an antigen through its T-cell receptor if it doesn’t get a second “go-ahead” signal from innate immune cells the T cell either:
Becomes inactive (this is called anergy), or
Undergoes programmed cell death (apoptosis).
How T cells get activated:
1) Their T-cell receptor (TCR) must recognize and strongly bind to an MHC/peptide complex (this shows them what to attack).
2)They also need a “go-ahead” signal, called co-stimulation, which usually comes from a protein called CD28 on the T cell binding to B7 molecules
(At first, T cells have a lot of CD28 on their surface to help them get that co-stimulation signal.
However, as the T cells keep getting stimulated (encountering the antigen), they start putting a different protein, CTLA-4, on their surface.
CTLA-4 competes with CD28 for the same B7 molecules, but CTLA-4 binds B7 1,000 times better than CD28)
When CTLA-4 binds to B7, it takes away the opportunity for CD28 to get the “go-ahead” signal.
This blocks CD28’s ability to fully activate the T cell. In other words, CTLA-4 slows down or stops the T cell from continuing to attack by reducing the number of B7 molecules available.
