Innate Immune System Flashcards
3 main components of innate immune system
- Physical Barriers
- Cells
- Soluble Mediators
What are the physical barriers?
Skin and mucosa
How does the skin act as a physical barrier?
Physical barrier, physiological conditions, Glands
How do mucosal surfaces act as barriers?
Mucus and Cilia
What are the cells of the innate immune system?
Granulocytes (Neutrophils, basophils, mast cells, eosinophils), Monocytes→macrophages, Dendritic cells, NK cells
Granulocytes and their function
Neutrophils - Phagocytosis,
Basophils and Mast cells histamine,
Eosinophils - parasites
Monocytes/macrophage function
Monocytes → migrate to tissue → macrophages → phagocytosis and antigen presentation to T cells
Dendritic cells, their function and what do they express
Antigen presentation
After phagocytosis → migrate to lymph nodes → activate CD4+ and CD8+ T cells
Fc - complexes
Cytokines - regulation
NK cells and their function
Kill malignant/viral cells
inhibition - self-HLA
activation - heparan sulphate proteoglycans
What soluble mediators are in the innate response
Cytokines and complement
Key cytokines and their roles
TNF-alpha, IL-1(fever) - main, initiators
Chemokines - leukocyte recruitment
IFNs - viruses
Complement and their role
Tightly regulated soluble factors inactive in blood
Once activated: Opsonisation, Vasodilation + increased vasc permeability, Chemo attraction, activation of leukocytes, MAC
How is C3 activated?
Classical: Antigen binds antibody → C1 activated →C2, C4 activated which activate C3 convertase
MBL: MBL binds carbs on bacterial surface → C2, C4 activated which activate C3 convertase
Alt: C3 binds to bacterial cell wall components (LPS) → C3 autoactivation
C3 activation to MAC formation to bacterial killing
C3 activation → final common pathway C5-9 → MAC formation → MAC makes pores in bacteria
Steps of innate immunity before pathogen killing
- Phagocyte recruitment
- Microorganism recognition
- Opsonisation → endocytosis
- Phagolysosome
Phagocyte recruitment process
Cellular damage and bacterial products → local cyto/chemokines production
Cytokines → increased vascular permeability
Chemokines → attract phagocytes
Microorganism recognition process
TLR and MR - recognise PAMPs
FcR - immune complexes
Opsonin examples
Antibodies binding to FcR
Complement components binding to CR1
Acute phase proteins
Microbial Killing mechanisms
- Oxidative
NADPHo → ROS (superoxide and H2O2)
MPO - H2O2 + Cl- → HOCl
HOCl kills - Non-oxidative
lysozyme and lactoferrin in different specific granules → broad coverage
Phagocyte death process and abscess formation
Neutrophil glycogen depleted → cell death → release of residual enzymes → liquefaction → pus formation (dead neutrophil accumulation) → abscess formation
