Introduction to Innate Immunity Flashcards
1
Q
Describe innate immunity
A
- First line of defence
- Rapid and generalised - not pathogen specific
2
Q
What are the components of innate immunity?
A
- Epithelial barriers
- Soluble mediators - chemokines, cytokines, complement
- Cellular mediators - phagocytes, dendritic cells, NK cells
- Antimicrobial peptides
3
Q
Describe adaptive immunity
A
- Second line of defence
- Delayed and specific
- Has immunological memory
4
Q
What are the components of humoral immunity?
A
- B cells
- Antibodies
5
Q
What are the components of cellular immunity?
A
T cells
6
Q
Describe PAMPs?
A
- Structures or types of molecules not present in the host
- Signal of “foreign-ness”
- Shared among microbial species (but not all) - present even in pathogens invading host species for the first time
- Nucleic acids
- Structural motifs
7
Q
What nucleic acids can act as PAMPs?
A
- ssRNA - no cap as human’s mRNA are capped so exposed 5’ - strong initiator of the immune response in viral
- dsRNA - replication intermediates and structures which are almost never present in humans - all viruses produce dsRNA as an intermediate
- DNA - in the cytoplasm triggers the immune system - unmethylated CpG in viral DNA with CG repeats
8
Q
What structural motifs act as PAMPs?
A
- Glycoproteins on virions
- Capsid proteins
9
Q
Describe the interferon system
A
- Virus enters a cell and produces PAMOs which are detected by pattern recognition receptors
- Induces interferon and signals to another cell
- Interferon induces another signalling cascade in the new cell - activates interferon stimulated genes
- ISGs make antimicrobial peptides and other effectors that induce an overall antiviral state in the cell
- Usually the infected cell dies but the neighbouring cells can’t be infected or can’t replicate virus and so survive - stops the spread of the virus
10
Q
What cytoplasmic nucleic acid sensors induce the interferon system?
A
- dsRNA and other RNAs are detected by RLRs - causes a signalling cascade that activates a TF complex composed of IRF3 and IRF7 and then induces IFN
- dsDNA are detected by cyclic GMP-AMP synthase (cGAS) - signals via STING to activate the IRF3 and IRF7 complex and then induces IFN
11
Q
What do membrane-bound TLRs detect?
A
- TLR9 senses CpG DNA - normally not present in human cells
- TLR8 senses ssrRNA
- TLR3 senses dsRNA
12
Q
How does IFN signal to neighbouring cells?
A
- IFN binds to the IFN receptor
- Get the recruitment and phosphorylation of Tyk2 and Jak1
- These phosphorylate TFs called STAT1
- STAT1 dimerises and moves into the nucleus
- STAT1 recruits IRF-9
- Induces ISGs
13
Q
What symptoms does IFN cause?
A
- Fever
- Chills
- Generalised aches and pains
- Headache
- Poor appetite
- Fatigue
- Drowsiness
