Infection Session 3- Lecture 2- Innate Immune System Flashcards
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
