π Effector Mechanisms of Innate Immunity Flashcards
(16 cards)
What is phagocytosis and which cells are phagocytic?
Engulfment + digestion of extracellular material
MPs, DCs, Ns, monocytes
What are the steps of phagocytosis?
- Phag detects path thru PRRs/opsonins β binds
- Phag extends PM around path β internalises pathogen in phagosome
- Phagosome fuses w lysosome β phagolysosome β exposed to lysosomal enzymes, ROS, Dec pH β breakdown
- Residual undigested material β expelled + some Ags may be processed β presented on MHC mols to T cells
What is opsonisation and how does it enhance phagocytosis?
Coating of pathogens in opsonins (Ab, cβ) β binds Fc receptors/CRs on phag cells β triggers phag
Which molecules act as opsonins?
Ab
Cβ
What are Fc receptors and how do they promote phagocytosis?
Membrane bound receptors on phag cells surfaces
Bind constant region of Ab β trigger intracellular signalling pathways β engulfment + destruction of MO
How do complement receptors aid in pathogen uptake?
CRs = membrane bound receptors on phag cells
Bind cβ (e..g C3b) on opsonised pathogens β trigger intracellular signalling paths β engulfment + destruction of MO
What are neutrophil extracellular traps (NETs)?
Web-like protein structures secreted by Ns β immobilise MOs for IC targeting + prev spread
Composed of:
- dna
- Antimicrobial peptides
- histones
What is the role of NK cells in killing infected or cancerous cells?
Recog β MHC I expression
β release performing + grazymes β induce apop
β prod IFN-Ξ³ β activate MPs + promo Th1 response
How do NK cells recognise βmissing selfβ?
Re: balance b/w inhibitory + activating receptors
- Inhibitory receptors β bind normal MHC I β inhibit killing
- Activating receptors β detect stress ligands β trigger killing
Killing triggered when activating > inhibiting
What is the role of perforin and granzymes in NK cell killing?
Perforin β forms pores
Granzymes β induces apop
What cytokine is secreted by NK cells and what is its role?
IFN-Ξ³ β activate macrophages + promote Th1 response
What is the function of mast cells in early inflammation?
Located in tissues - early responder
Degranulation β release histamine β initiate inflammation
How do eosinophils contribute to anti-parasite defence?
Degranulation β release cytotoxic granules
How do innate cells promote inflammation?
Release Ck + histamine
What are chemokines and how do they regulate cell recruitment?
Sml signaling proteins in plasma
Form conc grad β guide ICs to infection site
2 types:
- CC β mostly recruit monocytes
- CXC β mostly recruit Ns
What is the role of macrophages beyond phagocytosis?
APCs β pres processed Ag to T cells β activ + diff into th1/2 β help b cells β prod Ab
Secrete Ck β inflamm, recruit
