T Cells Flashcards
What type of T cell helps other cells but must get permission to do so?
Helper T cells
What type of T cell kills other cells but must get permission to do so by way of a cognate antigen?
Killer T cells
Where do T cells mature?
Thymus (T for thymus)
From where are white blood cells made?
Bone marrow
Where do T cells circulate?
Blood and lymph
What is the function of T cell receptors located on the surface of T cells that are “antibody like receptors”?
Specialize in recognizing protein antigens presented by MHCs (antigen = peptide)
How many T cells are in the body?
About 300 billion
What is another name for killer T cells?
Cytotoxic T cells (CTLs)
What activates killer T cells?
MHC I
How do killer T cells kill other cells?
Trigger them to commit suicide (therefore killing the virus inside, as well)
What activates helper T cells?
MHC II on APCs
What type of T cell can secrete cytokines?
Helper T cells
What cells keep the immune system from overreacting?
Regulatory T cells
<p>What cytokines can be released from helper T cells?</p>
<p>Interleukin 2 (IL-2), TNF,and interferon gamma (IFN-gamma)</p>
What type of T cell is activated by MHC I being presented on cell surfaces?
Killer T cell (CTLs)
What type of T cell is activated by MHC II being presented on APCs?
Helper T cells
What is required in order for helper and killer T cells to function?
Activation
What is the function of the T cell receptor?
Recognizing the cognate antigen
What is the function of the co-receptor?
Recognizing the MHC (I or II)
What is the purpose of co-stimulation?
Recognition of other molecules
More is known about activation of which T cell, overall?
Helper T cell
What happens to a T cell when it sees “self” being presented by other cells?
It dies (deemed unnecessary)
What happens to a T cell if it recognizes self antigen but doesn’t get co-stimulated?
It will be rendered inactive (anergized) and will eventually die
What happens to a T cell if it sees “nonself” and gets co-stimulated?
It therefore becomes activated
When the usual process of a T cell dying when recognizing “self” does not occur and the T cells remain, what issue can result?
Autoimmune disease
Is a T cell receptor the same as an antibody?
No; they are antibody-like
Which is more diverse: T cell or B cell receptors?
B cell receptors
What type makes up the majority of T cell receptors (95%)?
Alpha-beta (traditional)
Are all T cell receptors on mature T cells identical?
Yes, for the most part (but may be some exceptions)
What is the name given to the group of signaling proteins?
CD3
What is the non traditional type of T cell receptor?
Gamma-delta (make up 5%)
Where are nontraditional T cell receptors most abundant in the body?
Intestine, uterus, and tongue
Which have less diversity: traditional or nontraditional T cell receptors?
Gamma-delta (nontraditional)
What is the purpose of the CD3 proteins?
Signaling
What is the purpose of TCR proteins like alpha and beta?
Antigen recognition
What is the function of the co-receptor like CD4 or CD8?
MHC recognition and solidifying the bond
B7 is what kind of molecule needed to activation of T cells?
Co-stimulatory molecule
Which co-receptor is usually expressed on helper T cells?
CD4
Which co-receptor is usually expressed on killer T cells?
CD8
Which co-receptor attaches the TCR to MHC II molecules?
CD4
Which co-receptor attaches the TCR to MHC I molecules?
CD8
Which co-receptor sends a “likely to help” signal?
CD4
Which co-receptor sends out a “likely to kill” signal?
CD8
When do T cells express both co-receptors (CD4 and CD8)?
When they are in the thymus (immature)
What is the function of the MHC?
Presents the antigen
What is the function of the peptide?
Antigen
What is the function of the TCR?
Recognizes the peptide antigen
What is the function of CD3?
Sends a signal to the nucleus
B7 is expressed on the surface of what cells as a co-stimulatory molecule?
Antigen presenting cells
CD28 is a receptor molecule located on what cell?
T cell
What is the function of CD28?
When activated, it amplifies the signal and lowers the number of TCR crosslinks needed for activation
What does the combination of co-stimulation molecules depend on?
The pathogen involved and the area of the body
When do lipid rafts form?
When T cells become experienced during activation by co-stimulation
What is the function of the lipid raft formation?
Signaling of the nucleus because they contain large numbers of signaling molecules (making activation easier)
Why don’t experienced T cells need co-stimulation for reactivation?
It’s easy thanks to the formation of lipid rafts
What type of cell can deactivate T cells in a lymph node?
Dendritic cells
What cells can restimulate a T cell at the battle site?
Macrophages
What cells constantly scan dendritic cells in lymph nodes?
Helper T cells
What is an immunological synapse?
Adhesion molecules binding the two cells together once a cognate antigen is found
What attachment can lengthen the life of the dendritic cell?
CD40L protein and CD40 (on the dendritic cell)
How long does complete activation of the helper T cell take?
4-10 hours
What substance made by an activated helper T cell works as a positive feedback loop for division?
IL-2
What type of T cells don’t have IL-2 receptors?
Naive T cells (process starts once cognate antigen is found which doesn’t happen the majority of the time)
What are the communication proteins for the immune system?
Cytokines
Cytokines are also important in what other body systems?
Endocrine and nervous systems
What type of T cells are known for being cytokines factories?
Helper T cells
What are the three major subsets of cytokines?
Th1, Th2, and Th17
LPS is characteristic of what kind of bacteria?
Gram negative bacteria
What cytokines are formed from Th1 helper T cells?
Classical cytokines (TNF, IFN-gamma, IL-2)
What kind of attack stimulates Th1 helper T cells?
Viral or bacterial attack
What response does TNF promote?
Inflammation
What effect does TNF have on macrophages?
Activates infected macrophages and natural killer cells
IL-2 has what effect on natural killer cells?
Recharges them
What effect does IFN-gamma have on macrophages?
Keeps them activated
What kind of attack stimulates Th2 helper T cells?
Parasitic attack or food contaminated with pathogenic bacteria
What is the response involving Th2 helper T cells?
Intestines being under attack
When the intestines are under attack (Th2 cells), what interleukins are released?
IL-4, IL-5, IL-13
What is the goal of Th2 helper T cells?
Provide help to B cells for antibody production, especially class switching to IgE
What is the function of IL-4?
Growth factor to proliferate T cells (releasing Th2 cytokines) and is also a growth factor for B cells making IgE
What is the function of IL-5?
Causes B cells to make IgA (antibacterial in the GI)
Which interleukin stimulates mucus in the intestine?
IL-13
What kind of attack stimulates Th17 helper T cells?
Fungal and some extracellular bacteria
What causes helper T cells to bias toward a Th17 cell?
Dendritic cells making TGF-beta and IL-6
What is the response associated with Th17 helper T cells?
Enhance neutrophil response (harsh chemistry and phagocytosis)
What interleukins are produced with Th17?
IL-17 and IL-21
What is the function of IL-17?
Recruits massive numbers of neutrophils to the area
What is the function of IL-21?
Causes growth of more Th17 cells
Where do TFH (follicular helper T cells) cells reside?
Lymphoid follicles
What interleukin is produced by follicular helper T cells?
IL-21
How are Th17 and follicular helper T cells related?
They both produce IL-21
What is an area of proliferating B cells called?
Germinal centers
What cells are important for the formation of germinal centers to eventually regulate B cell differentiation into plasma and memory B cells?
Follicular helper T cells
What kind of helper cells are unbiased when first activated and can become any type?
Th0 helper T cells
IL-12 release from a macrophage stimulates the formation of which bias?
Th1
IL-6 and TGF-beta released from antigen presenting dendritic cell leads to which bias?
Th17
When does a helper T cell become committed to a certain bias type?
When it starts making a certain type of cytokine
How do helper T cells control the size of a response?
By dictating the number of killer T cells being made through the production of cytokines
What is the function of perforin?
Pokes holes in the membrane
What is the function of granzyme B?
Initiates a chain reaction leading to target cell suicide
What two packages do CTLs/killer cells deliver to kill a cell?
Perforin and granzyme B
What type of protein signaling initiates cell suicide by the killer T cells?
Connect a Fas ligand from the CTL to the Fas protein on the target cell
What makes the granzyme B easily injected into the cell by CTLs?
The protein perforin that makes the holes in the membrane
Which is a neater death of cell where the vesicles are eaten and disposed of by macrophages: necrosis or apoptosis?
Apoptosis
Which is extremely damaging and the enzymes and chemicals from the dying cell are released into the surrounding tissue resulting in inflammation: necrosis or apoptosis?
Necrosis
Compare the receptors of B and T cells
B cell receptors = light and heavy chains
T cell receptors = alpha and beta recognition protein
IL-12 is associated with what Th bias?
Th1
TGF-beta and IL-6 are associated with which Th bias?
Th17
What Th bias is present in utero?
Th2
What is the Th bias switched to at birth?
Th1
