Innate immunity Flashcards
What are the cells involved in innate immunity?
Macrophages, neutrophils, dendritic cells, natural killer cells, mast cells, basophils, eosinophils
What are the barriers in innate immunity?
Skin: low pH
Mucous membranes: blockage of attachment sites, shedding
Tears: lysozyme
Gut: acid, low pH
Normal flora or commensals (gut/skin): prevent attachment, produce bacteriocins, maintain epithelial barrier integrity, compete for nutrients
What is a main risk factor for infection?
Breached barriers (e.g. burn, drip, catheter, exposed wound etc)
How are pathogens recognised by innate immune cells?
Pathogen Associated Molecular Patterns (PAMPs) are conserved molecular patterns shared by broad classes of pathogens (normally absent in a sterile environment). These are not shared with their host; are shared by many related pathogens (nonspecific); are relatively invariant; that is, do not evolve rapidly.
Pattern Recognition Receptors (PRRs) recognize PAMPS.
Receptors on responding cells are not unique to that cell but are expressed on all sentinel cells of innate immune system.
What are the main characteristics of innate immunity?
Rapid response
Fully active without history of previous encounter with pathogen
Recognise broad classes of microbes
Does not confer long-lasting immunity
Perfect ability to distinguish between self and non-self
How do antimicrobial peptides work?
Antimicrobial peptide function by attacking pathogens or impeding their replication
Example: Defensins which target bacteria, yeast and enveloped viruses are found in macrophages, dendritic cell, neutrophil and epithelial cells.
What are Type I interferons?
They are cytokines that can be produced by almost all nucleated cells in response to viral infections. They interfere with viral replication in neighbouring cells. Example: IFNα, IFNβ
What are the phagocytic cells?
Neutrophil, macrophage, and dendritic cell
How do natural killer cells work?
NK cells are cytotoxic. Granules in their cytoplasm contain proteins such as perforin and proteases knowns as granzymes that will trigger apoptosis or cell lysis in an abnormal cell. They are activated by interferons and macrophage/dendritic cell- derived cytokines including TNFα and IL-12.
What is the purpose of inflammation?
- Deliver additional effector molecules and cells to site of infection to augment the killing of invading microorganism by macrophages.
- Prevent the spread of infection.
- Promote the repair of injured tissue.
What do neutrophils, basophils and eosinophils target respectively?
Neutrophils: bacteria, inflammation
Basophils: allergic response
Eosinophils: parasites
What is the function of the complement system?
- Opsonisation (targeting for destruction/removal) that enhances phagocytosis
- Inflammation through recruitment and activation of immune cells
- Complement‐mediated cytotoxicity through the formation of membrane-attack complex (MAC)
What is phagocytosis induced by?
It is induced upon ligation of many of the cell-surface receptors that recognize pathogens
