Adaptive Immunity, MHC, B-Cells, T-Cells (complete) Flashcards
What are the three main ways that adaptive immunity is different from innate immunity
- instead of a limited number of receptors, lymphocytes have 1 receptor will nearly infinite possibilities
- delayed onset, a few days
- immune memory = next exposure is better/faster
how many type of receptors does each t cell have
1
What is the MHC
major histocompatibility complex
what are the two types of MHCs
class 1 antigens class 2 antigens (there are also class 3, but they aren't as important to immunity)
where do you find class 1 MHCs
almost all nucleated cells
where do you find class 2 MHCs
only in APCs (antigen presenting cells)
what do class 1 MHCs do
hold a peptide fragment from an intracellular protein to present it to a T-cell (cytotoxic T-cell, CD8)
what do class 2 MHCs do
hold a peptide fragment from an extracellular protein to present it to a T-cell (helper T-cell, CD4)
which class of MHC works on endogenous antigens, and which class of MHC works on exogenous antigens
class 1 works with endogenous antigens class 2 works with exogenous antigens
what two things can the presentation of endogenous peptides from MHC class 1s tell you about the cell
- it can show “self” proteins and show that the cell is self
- it can show viral proteins and show that the cell has been infected
what does the presentation of exogenous peptides from class 2 MHCs tell you
it is only on cells involved in the immune response, and helps target things that shouldn’t be in our systems
From where do you get peptides that class 1 MHC’s present, and who do they specifically present them to?
they come from the cytosol and “talk” to Cytotoxic T-cells
from where do you get the peptides that class 2 MHCs present, and who do they specifically present them to>
they come from endosomal compartments (exogenous) and are taken from there to the cell surface by MHC class 2s. they “talk” to Helper T-cells
what is the human analog of MHC
HLA
what are immature dendritic cells like
- effective phagocytes
- low class 1 MHC
- no class 2 MHC
- recognize cytokines
what are mature dendritic cells like
- less phagocytotic activity
- high MHC levels (both classes)
How do dendritic cells mature
- on their own (spontaneous maturation)
2. by phagocytosing a microbe
do spontaneously matured dendritic cells activate naive T-cells
nope
do activated matured dendritic cells activate naive T-cells
yes, maybe the only thing that can do so effectively
how do matured Dendritic cells activate naive-t cells
- microbes and macrophages cause IL-1 and TNF
- IL-1 and TNF cause mature dendritic cells to migrate to secondary lymphoid structures
- they express high levels of MHC, B7-1 and B7-2
- those interact with CD4 T-cells
(need the T-cell to bind BOTH the MHC, and the B7s)
what is important in determining compatibility of tissue grafts
MHCs
what makes dendritic cells hone to secondary lymphoid tissue
CCR7
what on naive T-cells looks for the B7-1 and B7-2 on activated mature dendritic cells
CD28
how do the peptide grooves of MHC class 1 and 2 molecules differ
class 1 has capped ends and only allows shorter peptides. it also uses one protein as both sides of the binding groove class 2 doesn't have capped ends and can allow longer peptides. it uses two separate proteins as the sides of the binding groove
are all MHC class ones the same
no, there are many different class 1 MHCs ( the same for class 2 MHCs) thats why they can cause problems in acceptance of a grafted tissue
what is the most gene dense region of the human genome
the MHC gene region
how are MHC alleles expressed
codominantly (both the mom and dads MHCs are expressed)
if a human and mouse have three MHC 1 proteins, how many different MHC 1’s can they have on a given cell
6 Ad Am Dd Dm Ld Lm
d= from dad m = from mom
if a human has three MHC class 2 proteins (a dimer) how many different MHC 2s can they have on a given cell
12
if a mouse has three MHC class 2 proteins (a dimer) how many different MHC 2s can they have on a given cell
8
if some species is found to have 4 MHC class 2 proteins (a dimer) how many different MHC 2s could they have on a given cell
16
(5 = 20)
(6=24)
what do classical MHCs do?
what do non-classical MHCs do
classical present peptide antigens to T-cells
non-classical do anything else
where do you find the polymorphisms in class 1 and 2 MHCs
in the peptide binding grooves
what helps the intermediate immune response between innate and adaptive immunity
non-classical MHCs
what is CD1
a non-classical MHC that presents mycobacterial glycolipids to specialized T-cells
what enzyme creates the endogenous peptides that are presented by class 1 MHCs
proteasomes
what is the process of creating peptides that MHC class 1s will present to cytotoxic CD8 t-cells
- ubiquitin tags the intracellular protein
- Proteasomes cleave the peptide in the cytosol
- peptidem moves into the ER lumen
- it binds to MHC 1 and this creates a vesicle
- then it is transferred to the cell membrane
what is the difference between constituative proteasomes and immunoproteasomes
immunoproteasomes cut peptides into better lengths for MHC class 1s
what are DRiPs and how do they relate to MHCs
they are defective ribosomal products, and they are usually marked by ubiquitin and cut up by proteasomes, then bound to MHC1 and sent to the membrane
what happens to MHC1s that don’t bind a peptide in the ER
they are broken down eventually
how can viruses counteract their destruction by MHC1s
they can stop the process of MHCs binding peptides, and moving to the membrane, so cytotoxic T-cells don’t attack them
how does herpes virus prevent being killed by cytotoxic t-cells
they stop the MHC 1 from binding peptides and moving to the surface
how does the body kill cells that have overcome the MHC1s ability to signal for their destruction
NK cells can recognize the low MHC class 1 levels and will destroy the cell
what do helper T-cells do once they have been presented the peptide fragment from MHC class 2
- they show it to macrophages (this activates them to be more efficient killers)
- they show it to B-cells (this causes them to differentiate and expand into plasma cells, these create antibodies)
how are class 2 MHC’s loaded with peptides
- MHC 2 in ER is blocked by invariant chain
- in a vesicle the invariant chain degrades, leaves CLIP fragement
- Exogenous antigen is taken up
- HLA-DM switches the antigen and CLIP
- it is transported to the membrane
what on the T cells helps recognize the MHCs that are presenting peptides to them
- TCR (T-cell receptor)
- either CD8 or CD4
(if CD8 = cytotoxic T-cell, binds MHC 1)
(if CD4 = helper T-cell, binds MHC 2)
what to TAPS do
takes the peptides from the proteasomes and puts them back into the ER, and binds them to the MHC
what is cross presentation of exogenous antigens
exogenous antigens that are redirected into the enogenous presentation pathway. exogenous peptides with MHC class 1.
what cells do cross presentation of exogenous antigens
dendritic cells
what does cross presentation of exogenous antgens do
causes CD8 cytotoxic t-cells to be primed by exogenous antigens (instead of endogenous)
