Infection Session 3- Lecture 2- Innate Immune System Flashcards
(22 cards)
What factors determine the outcome of the host-pathogen relationship?
- Pathogen: infectivity
- Patient: host’s immune response
- Mechanism: virulence (ability of pathogen to damage host
- Give a definition for the immune system
- Give a definition of infectious disease
- Cells and organs that contribute to immune defences against infectious and non-infectious conditions (self vs non self)
- When the pathogen succeeds in evading and/or overwhelming the host’s immune defences
Give four points on how the immune system protects us
- Pathogen recognition: cell surface and soluble receptors
- Containing/eliminating the infection (containing at site to prevent systemic infection)
- Regulating itself (ie inflicting minimal damage to host)
- Remembering pathogens (prevents the disease from recurring)
Contract the types of protection that is given by innate and adaptive immunity
- Innate: immediate protection, is very fast (seconds), lacks specificity or memory, no change intensity
- Adaptive: long lasting protection: slow (days), is specific and has immunological memory and changes in intensity
What are 4 factors/barriers that prevent entry and limit growth of pathogens? (Thus preventing systemic infections)
- Physical
- Physiological
- Chemical
- Biological
What are the physical barriers?
- Skin
- Mucous membranes: mouth, resp tract, GI and GU tract
- Bronchial cilia: expels microbes trapped within mucus, anything that compromises cilia can lead to infection
Give 4 physiological barriers
- Diarrhoea: food poisoning
- Vomiting: food poisoning, hep, meningitis
- Coughing: pneumonia
- Sneezing: sinusitis
Discuss the chemical barriers
- Low pH: skin 5.5
- Antimocrobial molecules: IgA (tears, saliva, mucous membranes), lysosomes (urine), mucous
Explain the biological barriers in place and what their benefits are
- Normal flora: non pathogenic microbes in strategic locations (mouth/throat, etc), absent in internal organs/tissues.
- Benefits: compete with pathogens for attachment sites and resources, produce antimicrobial chemicals and synthesise vitamins (K, B12)
Give examples of normal flora being displaced from its normal location to a sterile location
- Breaching skin integrity: skill loss (burns)
- Fecal-oral route
- Fecal-perineal-urethral route: UTI
- Poor dental hygiene/dental work
What are the main phagocytes? Describe each
- Macrophages: present in all organs, ingest and destroy microbes through phagocytosis, antigen presenting to T cells and produce cytokines/chemokines
- Monocytes: present in blood –> recruited at infection site and differentiate into macrophages
- Neutrophils: present in blood, increased during infection, recruited by chemokines to site of infection –> ingest and destroy bacteria
Describe other key cells in innate immunity (not macrophages, monocytes or neutrophils)
- Basophils/mast cells: early actors of inflammation (via vasomodulation) and important in allergic rxns
- Eosinophils: defence against multi-cellular parasites (worms)
- Natural killer cells: kill all abnormal host cells (virus infected or malignant)
- Dendritic cells: present microbial antigens to T cells (acquired immunity) - produce long term defences
What are PAMPs?
What are PRRs?
What are these two things?
- Pathogen recognition microbial structures: pathogen associated molecular patterns (can be lipids, carbs, proteins, nucleic acids)
- Pathogen recognition receptors (PRRs): best one is Toll Like receptor (are on every cell surface and inside to recognise viruses which have invaded host cells) - important for phagocytes
- These two types of receptors are very important for recognition, for every PAMP there is a PRR on the phagocyte
Give an example of a microbial PAMP and PRR
- Gram positive bacteria PAMP: peptidoglycan
- PRR: TLR2
Apart from PAMPS and PRRs, what’s another pathogen recognition method?
-Opsonisation of microbes: coaching proteins called opsonins that bind to the microbial surfaces, leading to enhanced attachment of phagocytes and clearance of microbes
Give two examples of an opsonin
- Complement proteins: C3B
- Antibodies: IgG (IgG is very good, binds to microbe and phagocyte has receptors for it so it recognises that if IgG is bound to it, it should engulf the pathogen)
Describe what happens to phagocytes in terms of encountering a microbe and what should happen after
Phagocyte:
- Chemotaxis and adhere of microbe to phagocyte: recognises using PAMPs or opsonins
- Ingesting of microbe by phagocyte
- Formation of phagosome
- Fusion of phagosome with a lysosomes to form phagolysosome
- Digestion of ingested microbe by enzymes
- Formation of residual body containing indigestible material –> discharge of waste materials
Outline the seconds lines of defence of the innate immunity
- 1st line: barriers
- 2nd line: phagocytes, chemicals (complement system cytokines) –> these then lead to inflammation.
Outline the three most important pathways of complement system
- C3a and C5a: recruitment of phagocyte via chemotaxis
- C3b-C4b: opsonisation
- C5-C9: killing of pathogens with MAC
What are the two main functions performed by phagocytes?
- Phagocytosis
- Cytokines/chemokines: chemoattraction, phagocyte activation and inflammation
What are the 4 anti-microbial actions of macrophage derived TNF alpha/IL1, IL6
- Liver: raised CRP + complement activation
- Bone marrow: neutrophil mobilisation
- Inflammatory actions: vasodilation, vascular permeability + adhesion molecules (attractions of neutrophils)
- Hypothalamus: increase body temp
Give a disease/condition that would lead to
- Decreased spleen function
- Decreased neutrophil number
- Decreased neutrophil function
- Asplenic patients
- Cancer chemotherapy
- Chronic granulomatous disease (no respiratory burst)
