Lecture 8 Flashcards
What are APCs?
Cells to displaying MHCII
What cells express MHCI?
All necleated cells
How do APCs take up antigen?
Either phagocytosis or surface receptors
What are the APCs?
Macs
DCs
B cells
Another name for macrophage?
Mononuclear phagocytes
Another name for macrophage?
Mononuclear phagocytes
What are kupfer cells?
Macs found in liver
Name for macs in liver?
Kupfer cells
Macs found in brain?
Microglial cells
What are microglial cells?
Macs in brain
APCs in skin?
Langerhans cells
What are Langerhans cells?
APCs in skin between dermis and epidermis
Two types of dendritic cells?
Conventional
Plasmacytoid
What do Plasmacytoid dendritic cells do?
Produce large volumes of interferon in response to viral infection
Difference between mature and immature dendritic cells?
Immature are much more highly phagocytotic
When is B cell presentation most important?
Secondary antibody response
Difference between where MHCs find antigens?
MHCI - intracellular
MHCII - extracellular
What happens in early endosomes?
Proteases are inactive
Activate when they become acidic
What do endosome fuse with?
Vesicles containing MHCII
Where does MHCI bind antigen?
ER
Where are MHCI antigens synthesized?
Cytosol
Which MHC functions via phagocytosis?
II
What is usually presented in MHCI?
Molecules from viruses that have taken over cell machinery
What degrades MHC antigens?
Proteosomes in cytosol
Sub unitis of proteosome involved in degradation?
LMP2/7
What do Tap1/2 do?
Transport cytosolic antigens across ER
What do calnexin, ERP57, and calreticulin do?
Chaperons in ER helping with assembly of MHCI
What is ERAAP?
Trims peptides when the enter ER so they can be bound MHCI
What does calnexin do
Holds MHCI chain until B2 microglobin binds
What does tapasin do?
Holds MHCI to tap so can bind peptides
How are MHCII antigens processed?
Endosomes and lysosomes
How does MHCII antigen bind MHCII?
Endosome fuses with vesicle that has MHCII
What is an invariant chain?
Occupies MHCII binding site in vesicle
Degraded in acidic endsome leaving CLIP
What is CLIP?
Portion of invariant chain left behind in endsome
What releases CLIP?
HLA-DM
What does HLA-DM do?
Releases CLIP
What does MHCI do in absence of foreign antigen?
Presents self on surface
What does MHCII do under normal condition?
Contains CLIP, not self antigen like MHCI
Can CD4 recognize free antigen?
- NO
- Only antigen in MHCII on surface of APC
What does T cell, MHC interaction produce?
T cell proliferation and differentiation
What can CD4 cells do?
Mediate macrophage activation
Act as helper cell in antibody response by secreting cytokines
What is Th1?
T cell that activate macs that have presented antigen
What T cells activate macs?
TH1
What is Th2?
Induce antibody synthesis when B cell presents
What T cells induce antibody synthesis?
TH2
What T cells induce antibody synthesis?
TH2
Characteristics of resting/immature CD?
Not good at antigen presentation
Good at phagocytosis
When do DCs mature?
During innate response and after eating something
What do mature D cells do?
- Present antigen well
- Produce cytokines necessary for T prolif/dif
- Present co stimulatory molecules
What are some costimulatory molecules?
B7
CD80/86
What is required for naive T cell activation?
Signal from MHC with antigen
Signal from B7/CD28
Where is B7 found?
Surface of APC
What does B7 interact with?
CD28 on T cells
Where is CD 28 found?
Surface of T cells
What happens when APC takes up antigen that is not microorganism?
B7 may not be expressed
What happens when no B7
CD40/CD40L process initiatated
How does APC/T interaction start if no B7
- T cell expresses CD40L
- Interacts with CD40 on T cell surface
- This induces B7 for costimulation activating T cell
Cells required for antibody productoin?
Both B and T cells
B cell APC?
- B7 activated on B cell when presents antigen in MHCII
- T cell recognize antigen and are activated
- T cell now expresses CD40L
- CD40 system causes T to release cytokines activating B
How long must naive T cells be engaged?
- Not long to begin signalling
- Minutes to hours for prolif/dif
What is immunlogical synapse?
Prolonged engagement of T cell with MHC allowing for diff/prolif
What facilitates immunological synsapse?
LFA1 - on T cell
ICAM1 - on APC
Where is ICAM1 found?
APC
Where is LFA2 found?
T cell
Where is LFA2 found?
T cell
Can TH1 activate B cell?
Yes but to a much lesser extent than TH2`
What are plasmacytoid dendritic cells?
Plasmacytoid dendritic cells - important in protection from virus
What is interferon?
Antiviral cytokine
Why do lymph nodes swell in strep?
Lymph nodes swell in strep throat as the are full of T cells that have been activated by antigens
Can CD4 recognize free antigen?
No, only in context of MHCII
Cytokine for TH1 response?
INFG
What is INFG important for?
TH1 response
What is IL4 inportant for?
TH2 response
What is cytokine for TH2 pathways?
IL4
When is B7 used?
Only if foreign partical is micro organism
B7 and CD40 always present on cell surface?
Only 40C
Can class switching occur without T cells ?
No