MCB Lecture 48 Cooperative Immune Response Flashcards
What are the two different types of T lymphocyte?
T cytotoxic, CD8+
T helper, CD4+
Describe (and point out the differences) between antigen processing for MHC I and MHC II
MHC I: endogenous protein (synthesised inside the cell, may be viral DNA)
- MHC I synthesised in ER, protein degraded into peptide by proteosome and delivered via vesicle to ER
- Peptide binds to the cleft
- MHC I - pep exported to surface in a vesicle
MHC II: exogenous protein
- Protein endocytosed, and degraded into peptides by phagolysosome
- MHCII synthesised in ER
- Invariant chain binds in the cleft to prevent peptide binding there
- MHC II loaded into vesicle, which fuses with phagolysosome.
- Peptide loaded into MHC II cleft, invariant chain displaced
- Transported to the surface via a vesicle
Compare the different proteins found on T lymphocytes
CD8, binds to conserved alpha-3 of MHC I
Cd4, binds to conserved beta-2 of MHC II
Differentiate between the type of MHC that both types of lymphocyte interact with
CD8+: MHC I
CD4+: MHC II
What is the function of CD8+?
Bind to and kill cells that have been infected by a pathogen, or neoplasticism cells
What is the function of CD4+?
Help B cells and macrophages
Moderate immune response
Briefly describe the process of activation of lymphocytes
Naïve lymphocyte -> Effector cell
What is a dendritic cell?
It is a professional antigen presenting cell
What is the normal function of an APC?
How does it do this?
It samples the environment via:
Macro-pinocytosis
Mannose-R
FcR
The protein it takes in via this sampling is degraded and presented in MHC II
How are APCs activated?
- PAMP binds to PRR (Licensing)
2. Endocytosis of pathogen
Describe the steps involved in APC and T lymphocyte interaction
- APC undergoes licensing and expression of invader peptide in MHC
- APC moves to the lymph node via lymphatics
- Once in lymphatics, the peptide expressed in the MHC is recognised by TCR on T lymphocytes, activating them
Outline the post-Licensing maturation events of an APC
Increased MHC I and MHC II expression Stop sampling Migration to lymphoid tissue Expression of co-stimulatory and adhesion molecules Secretion of cytokines
What is licensing?
This is when an APC becomes active after binding a PAMP of an invading pathogen
What is signal one?
This is the binding of T lymphocyte and APC, via the TCR and MHC
What is signal 2?
APC cost insulate T cells, causing them to proliferate