L7 Innate Immunity Flashcards
(20 cards)
What is innate immunity?
The recognition of antigens by non-specific Pattern Recognition Receptors
Receptors are germline encoded
What are the functions of innate immunity? [3]
Prevent infection
Promote acute inflammation
Respond rapidly
Innate mechanical barriers to infection
Skin: Epithelial cells joined by tight junctions. Longitudinal flow of air or fluid
Gut: Epithelial cells joined by tight junctions. Longitudinal flow of air or fluid
Lungs: Epithelial cells joined by tight junctions. Movement of mucus by cilia
Eyes/nose: Epithelial cells joined by tight junctions.
Innate chemical barriers to infection
Skin: FA and antibacterial peptides
Gut: Low pH and enzymes (pepsin) + antibacterial peptides
Eyes/nose: Salivary enzymes (lysozymes)
Innate microbiological barriers to infection
Skin: Normal flora
Gut: Normal flora
How do the antigen receptors of innate immunity work?
Antigen receptors of innate immunity detect antigens non-specifically using receptors for ‘pathogen-associated molecular patterns’ (PAMPS)
PAMPS are patterns of molecules that occur in lower organisms, but do not occur in humans
These receptors are called pattern recognition receptors (PRRs)
This is an effective mechanism for distinguishing self from non-self
What are toll-like receptors?
Toll-like receptors (TLRs) are an example of a pattern recognition receptor. Drosophila with TLR mutations were susceptible to fungal infection
What is MBL?
Mannose binding ligand
Example of PRR
Binds with high affinity to mannose and fucose residues with correct spacing
What do natural killer cells do?
NK cell recognises antibody-coated bacteria by Fc receptor; the target organism is then killed by non-phagocytic means
Process known as antibody-dependent cellular cytotoxicity (ADCC)
What are eosinophils?
Believed to be important in defence against parasites
Local infiltration at sites of infection
Numbers in blood increase during parasite infection
Granules contain toxic enzymes
Can perform antibody-dependent cellular cytotoxicity
Also found at sites of allergic inflammation
Cytokines and systemic inflammation - liver
Acute-phase proteins (C-reactive MBL)
Activation of complement opsonisation
Cytokines and systemic inflammation - bone marrow endothelium
Neutrophil mobilisation
Phagocytosis
Cytokines and systemic inflammation - hypothalamus
Increased body temperature
Decreased viral and bacterial replication.
Increased antigen processing.
Increased specific immune response.
Cytokines and systemic inflammation - fat, muscle
Protein and energy mobilisation to allow increased body temperature
Decreased viral and bacterial replication.
Increased antigen processing.
Increased specific immune response.
What is complement and what does it do?
Complement is a series of enzymes that are produced in the liver and circulate in the bloodstream
The enzymes circulate in inactive form
When the first enzyme is activated, it goes on to activate the next in the sequence, which then activates the next and so on
This is called a ‘triggered enzyme cascade’
What is opsonisation by complement?
Complement plays a role in opsonisation, along with antibody
Activated complement component C3b sticks to pathogens
Binds to phagocyte C3b receptors
What is alpha interferon and what does it do?
Soluble innate mediator
Production activated by viral infection
Work locally on surrounding cells
What are the antiviral effects of interferons?
Stop cells dividing
Stop cells synthesising new proteins
Stimulate production of anti-viral proteins by host cell
What is cell lysis by the terminal pathway?
Terminal pathway components assemble a ‘pore’ which inserts into pathogen membranes
What are the interactions between innate and adaptive immunity?
Inflammation attracts T and B cells to local lymph nodes for activation
Innate immunity a key effector mechanism for antibodies
- Opsonisation/ phagocytosis
- Antibody-antigen complex/ complement
- Mast cells
Innate immunity is also directly required to activate T cells;
