Innate Immunity 1 Flashcards
What are the 3 main parts of immunity?
- Innate immunity
- Early induced response
- Adaptive immune response
What are 5 main parts of innate immunity?
- Anatomic barriers
- Physiological barriers
- Phagocytic barriers
- Complement systems
- Inflammatory barriers
Why is adaptive immunity diverse?
Different antibodies are produced dependent on the pathogen
What 2 things are cross overs between innate and adaptive reponses?
- Helper T cells
2. Natural Killer T cells
What are 4 hall marks of the innate immune response?
- Rapid
- Non-specific
- First line of defence
- Not enhanced by repeated exposure
What are the 3 main divisions of natural defences of the immune system?
- Mechanical
- Chemical
- Microbiological
Describe 3 mechanical barriers which form part of the natural defence and where they occur
- Epithelial cells joined by tight junctions (skin, GIT, lungs, eyes/nose)
- Longitudinal flow of air and fluid (skin, GIT)
- Movement of mucus by cilia (lungs)
Describe 5 chemical barriers which form part of the natural defence and where they occur
- Fatty acids (skin)
- Low pH (GIT)
- Enzymes - pepsin (GIT)
- Antibacterial peptides (skin, GIT, lungs)
- Salivary enzymes - lysozyme (eyes/nose)
Describe a microbiological barriers which form part of the natural defence and where they occur
Normal flora (skin, GIT)
What microbicidal factor is secreted in the eyes?
Lysozyme
What microbicidal factor is found in the respiratory tract?
Mucus
What microbicidal factor is found in the stomach?
Acid
What microbicidal factor is found in semen?
Spermine
What microbicidal factor is found in the skin?
Sebaceous gland secretions
Name 5 major salivary components
- Histatins
- Lysozyme
- Lactoferrin
- Mucin 2 (MG2)
- Mucin 1 (MG1)
Name 6 functions of saliva
- Anti-microbial
- Buffering
- Digestion
- Mineralization
- Tissue coating
- Lubrication
Name 4 antimicrobial peptides in saliva
- Alpha-defensins HNP 1-4
- LL-37
- Beta-defensins hBD1 hBD2 hBD3
- Histatins
Give the origin, role and microbial targets of alpha-defensins HNP 1-4
- Neutrophils, gingival sulcus, sites of inflammation, salivary duct cells
- Antibacterial, antifungal, antiviral
- Candid albicans
Give the origin, role and microbial targets of LL-37
- Neutrophils, gingival sulcus, salivary glands and ducts
- Antibacterial
- S. mutans, F. nucleatum, A. actinomycetemcomi
Give the origin, role and microbial targets of beta-defensins hBD1, hBD2, hBD3
- Epithelia, salivary ducts
- Antibacterial, antifungal, antiviral
- hBD1 = Poor antibacterial, hBD2 and hBD3 = S. mustans, S. sanguis, F. nucleatum
Give the origin, role and microbial targets of histatins
- Salivary glands and ducts
- Antifungal
- Candida albicans
Name 4 salivary components with anti-fungal or anti-bacterial properties apart from peptides
- Lysozyme
- Lactoferrin
- Lactoperoxidase
- Mucins
What is the function of lysozyme?
Breaking down polysaccharide walls of many kinds of bacteria
What is the function of lactoferrin?
Combined with iron so prevents microorganisms from using iron from neutrophil granules
What is the function of lactoperoxidase?
Catalyses the oxidation of substrates which have potent bactericidal activities
What is the function of mucins?
Concentrate anti-microbial molecules at mucosal interface
What 5 things is the complement cascade important for?
1, Antibody response
- Cell lysis
- Phagocytosis
- Recruitment of neutrophils
- Clearance of dead cells
What are 4 responses produced by complement cascade?
- Increased vascular permeability
- Increased chemotaxis
- Increase anaphylaxis
- Increase phagocytosis
What are the 3 pathways of complement activation?
- Classical pathway
- MB-lectin pathway
- Alternative pathway
How does the classical pathway work?
Antigen-antibody complexes cause complement activation
How does the MB-lectin pathway work?
Lectin binding to pathogen surfaces cause complement activation
How does the alternative pathway work?
Pathogen surfaces cause complement activation
Give the steps of the formation of the MAC (membrane attack complex)
- C5b binds C6 and C7
- Complex binds to membrane via C7
- C8 binds to complex and inserts into membrane
- C9 molecules bind to the complex and polymerize
- 10-16 molecules of C9 bind to form pore in the membrane
What does a MAC lead to?
Cell lysis
Name 4 biological functions of the complement system
- Lysis
- Opsonization
- Activation of inflammatory response
- Clearance of immune complexes
Describe the process of opsonization during complement cascade
Complement proteins bind to bacteria causing them to be phagocytosed
Describe the process of inflammation during complement cascade
Mast cells bind to compliment proteins, degranulate and release histamine
Describe the process of clearance of immune complexes during complement cascade
Antibodies cause clumping of pathogenic cells which facilitates phagocytosis
What allows inflammation to occur?
Increase permeability of cells
How does dental plaque activate the alternative complement pathway?
C3a and C5a complement activation products in gingival crevicular fluid attract phagocytic cells through the junctional epithelium to the tooth crevice to attack bacterial plaque
Name 6 complement functions which are to the host’s benefit
- Opsonization enhances phagocytosis
- Phagocyte attraction and activation
- Lysis of bacteria
- Regulation of antibody responses
- Clearance of immune complexes
- Clearance of apoptotic cells
Name 2 complement functions which are to the host’s benefit
- Inflammation
2. Anaphylaxis
What is phagocytosis?
Uptake of large foreign particles as first line of defence against common microorganisms
What 2 things do activated macrophages secrete?
- Cytokines
2. Chemokines
How does phagocytosis work?
- Opsonization of particles and chemotaxis
- Binding of opsonized particles
- Internalization of particle by endocytosis (formation of phagosome)
- Fusion of phagosomes with lysosomes (macrophage) or granules (neutrophils)
- Degradation of internalized particles
- Formation of residual body, containing indigestible material, which is discharged from cell
What 3 substances are found in lysosomes and granules are released into phagolysosome?
- Proteinases e.g. elastase, lysozyme
- Binding proteins e.g. lactoferrin
- Anti-microbial peptides e.g. defensins
What are 2 methods of oposnization?
- Complement proteins
2. Antibodies
What are 4 methods of microbial evasion of phagocytic mechanisms?
- Inhibition of phagocytic absorption
- Inhibition of fusion of phagocytic lysosomes
- Survival inside phagolysosome
- Killing phagocytes after ingestion
