Innate Immunity Flashcards
Examples of mechanical factors (physical barriers)
skin, ciliary movement, peristalsis, washing by tears/saliva, mucus
Examples of chemical factors (physical barriers)
fatty acids - inhibit bacterial growth
lysozymes and phospholipases - inhibit growth of infectious agents
low pH - antibacterial effects
surfactant - enhance phagocytosis
microbiological factors (physical barriers)
healthy microbiome prevents infection by secreting inhibitory substances
Beta-lysine
part of coagulative system, released by platelets, bactericidal
Lactoferrin and transferrin
iron-sequestering molecules, prevent bacteria from stealing our iron
lysozyme
digests the bacterial cell wall
interferons
type I inhibit infection and replication of viruses
interleukin 1
increases temp. in inflammation and induces acute phase proteins
Neutrophils
most numerous innate immune cell, phagocytose and degrade pathogens. express CD66 marker.
2 types of neutrophil granules
Azurophilic: defensins to kill bacteria, proteolytic enzymes such as elastase, cathepsin G to degrade bacterial proteins, lysozymes to digest bacterial cell wall, myeloperoxidase
Secondary granules: found only in mature neutrophils. contain lysozymes, lactoferrin, NADPH oxidase (produces toxic radicals)
Macrophages
express CD14, CD11b, F4/80.
Kill with lysosomes. React to danger signals such as N-formyl-methionine, peptides of coagulative system, complement system, cytokines.
Phagocyte receptors to bind pathogens
Fc receptors - bind Fc region of antibody
Complement receptor - bind C3b
Scavenger receptor - bind polyamines on bacterial surface
TLRs - bind to PAMPs
Steps of phagocytosis
- Chemotaxis
- phagocyte detects and binds target
- phagocyte surrounds target object and engulfs via endocytosis
- endocytosed object enters a phagosome
- phagolysosome forms
- contents of lysosome released and digestion begins
Oxidative pathway of killing
Production of ROS or RNS to destroy endocytosed object
Non-oxidative pathway of killing
Cationic proteins - damages cell wall
Lysozyme - damage mucopeptides in cell wall
Lactoferrin - sequesters iron
Proteolytic and hydrolytic enzymes - digests bacteria
TLRs
recognize many different PAMPs (intra and extracellular). produce proinflammatory cytokines
NLRs
found only inside the cell, detect only intracellular pathogens or DAMPs
NOD1 - peptidoglycans
NOD2 - muramyl dipeptides
Causes activation of NFkB, leading to transcription of pro-inflammatory cytokines and IFNs.
RLRs
expressed in cytoplasm, detect viral DNA, induce production of IFNs
CLRs
bind carbs, involved in fungal recognition and immune modulation. Expressed by most cells
PGRPs
recognize peptidoglycans, induce production of antimicrobial peptides like defensins
Constitutively expressed in pigs
