Adaptive Immune Response Flashcards
How does a T cell kill a pathogen
An APC has to process the antigen - T cell can then bind and become active. Cytotoxic T cells kill the pathogen
Naive T cells cannot produce a response
Apc interacting with t lymphocyte (naive - not been activated by antigen yet)
amp gies 3 pieces of info
• invader
• what it looks like
• type o immune response
What are the features of APCs?
Features of Antigen Presenting Cells
• Strategic location (B and T cell interaction)
- Skin (SALT)
- Mucous membranes (GALT, NALT, BALT, GUALT)
- Lymphoid organs (Lymph nodes, spleen)
- Blood circulation (plasmacytoid and myeloid DCs)
• Pathogen capture - Phagocytosis (whole microbe) - Macropinocytosis (soluble particles) • Diversity in pathogen sensors (PRRs) - Extracellular pathogens (bacteria) - Intracellular pathogens (viruses)
Name different types of APC, their location, and the type of T cll they present to
Dendritic cells (lymph nodes, mucous membranes, blood) - naive T cells
Langerhans cells (skin) - naive T cells
Macrophages (various tissues) - effector T cells
B cells (lymphoid tissues) - effector T cells & naive T cells
Describe what happens once the APC recognises the pathogen
- Dendritic cells sense microbe PAMPS - tell T cells to activate the humoral immunity - best response to combat extacellular microbes
- antibodies - means there is complement activation and phagocytosis
How is a virus removed?
- viruses replicate inside cells - viral protein ins ide the cells dendritic cells have receptor
- only way to clear infection is to kill viral infection cells - kill all viral infected cells - cytotoxic cells
- hla??? Human version?? Mhc = mammalian??
What are class 1 and class 2 molecules on mhc/hla
Class I molecules Found on all nucleated cells - HLA A/B/C
Class II molecules Found on dendritic cells, macrophages, B cells - HLA-DP/DQ/DR
What are key features of MHC class i and ii molecules?
Key features of MHC class I and class II molecules
• Co-dominant expression
- Both parental genes are expressed
-> ↑ number of different MHC molecules
• Polymorphic genes
- Different alleles among different individuals
-> ↑ presentation of different antigens/microbes
• Main function
- MHC Class I: present peptides from intracellular microbes - MHC Class II: present peptides from extracellular microbes
• The more diverse the molecule the better ,the more diverse the microbe the immune response can be mounted against
• co dominant - 6 from each parent
• different alleleic varying - increase type of mucus - increase recognition - increases bility to activate T cells
Describe the structure of mhc class i and ii molecules
• Peptide binding cleft - Variable region with highly polymorphic residues • Broad specificity - Many peptides presented by the same MHC molecule • Responsive T cells - MHC class I recognized by CD8+ T cells - MHC class II recognized by CD4+ T cells
What are the 2 antigen processing pathways
Endogenous and exogenous
• Both self and non-self peptides are presented
• All peptides from the same microbe are presented by different MHC molecules
• Susceptibility to infections depends on the types of MHC molecules
What is the endogenous pathway
- When proteins produced in the cytoplasm - labelled for degradation - targeted - degrade by proteasome - uptaken by transporters - get into ER - expression of host Mhc class 1 - if you have right match for right mhc - makes a complex - complex shifted to cell surface - limitations.- if you dont have right Mhc, wont be able to present the right peptide
- Mhc class.1 on all cells - call cells can get infected
What is the exogenous pathway
• Exo - antigen always in vesicle - vesicles fused with lysosomes - gives small peptides - fuse with another vesicle - Mhc class 2 waiting there - if there is a right match be peptide and much 2 - stable and expressed at the cell surface
What are ltnps?
Some patients called Elite controllers or long-term nonprogressors (LTNP)
can control viral replication
What is the difference between slow/rapid progress or
Slow - mhc molecules present key peptides for the survival of the virus - effective T cell response
Rapid - mhc molecules present mutated peptides less critical for the virus - poor recognition by T cells so poor T cell response
What are the clinical problems with mhc molecules
• Major causes for organ transplant rejection
- HLA molecules mismatch between donor and
recipient (Allograft) - Graft-Versus-Host reaction (GVH)
• HLA association and autoimmune disease
- Ankylosing spondylitis
• HLA-B27 -> 90% of patients - Insulin-Dependent Diabetes Mellitus
• HLADQ2 -> 50-75% of patients
What are intracellular/extracellular microbes and whats the difference
Extracellular Microbes - Bacteria - Parasites - Worms - Fungi -> mhc class ii -> cd4 +t cells -> humoral (b cells nd complement)
Intracellular Microbes - Viruses - Bacteria - Protozoa
-> cd4 + T cells -> cell dependent immunity (b cells and complement)
cd8 + T cells -> cytotoxic T cells
