Immune System Overview Flashcards
What is reverse zoonosis
Human -> animal
What is CFR?
Case fatality rate
Mostly estimates and can depend on death recording methods, are rarely uniform over all population (underlying conditions)
Can influence risk vs hazard perception
Types of vaccines?
Live attenuated
Dead/subunit vaccines
Viral vectors
Risk and benefit of live attenuated?
-usually work well due to induction of strong immunity
-carry risk due to live nature, particularly for immuno-compromised
Risk and benefit of dead/subunit?
-Use part of microbe, usually safer
-don’t work as well as live attenuated and require adjuvants to induce strong protective immunity
What is a viral vector?
Genetically engineered microorganism used to deliver component (Ag?) for vaccine induced protection
Bad effects of immune system?
-immune pathology (collateral damage, allergies, autoimmunity)
-graft rejection
-metabolic diseases
-mental health
Obesity and immune system?
Leanness associates to type II response, obesity associated with inflammation and type I response
Immune system needs to:?
Detect pathogens, some of which not evolved yet
Distinguish harmful and harmless signals (pathogen Ag vs food)
Respond rapidly and eliminate pathogens using appropriate mechanism
Control strength of response to limit immune pathology
Barriers in Skin?
Mechanical:
-epithelial cells joined by tight junctions
-longitudinal flow of air or fluid
Chemical:
-Fatty acids
-Beta defensins, lamellar bodies, cathelicidin
Microbial:
-Normal microbiota (colonise niche so pathogens have no room to grow)
Barriers in Gut?
Mechanical:
-epithelial cells joined by tight junctions
-longitudinal flow of air or fluid
Chemical:
-Low pH
-enzymes (pepsin)
-alpha-defensins (cryptidins)
-RegIII (lecticidins)
-cathelicidins
Microbial:
-Normal microbiota
Barriers in lungs?
Mechanical:
-epithelial cells joined by tight junctions
-movement of mucus by cilia
Chemical:
-pulmonary surfactant
-alpha-defensins
-cathelicidin
Microbial:
-normal gut microbiota
Barriers in eye/nose/oral cavity?
Mechanical:
-epithelial cells joined by tight junctions
-tears
-nasal cilia
Chemical:
-enzymes in tears and saliva (lysozyme)
-Histatins
-beta-defensins
Microbial:
-normal microbiota
Pathogen methods of breaking barrier?
-Skin breaks, wounds, burns (Staphylococci, Streptococci, Clostridium tetani)(opportunistic)
-Animal bites (rabies)
-Insect bites (malaria, yellow fever, lymes disease)
-Parasites burrowing through skin (Schistosomes, hookworms)
Mucosal barriers difference to skin
Have to let things in (nutrients, gas exchange)
How does influenza exploit mucosal barrier?
Have receptors to bind and enter the cells, prevent ciliary motion to stop mucus movement out of body
What infections involve mucosal barriers?
Placenta
Lungs
STIs
Faecal-oral
Food-borne
Purpose of innate response?
Gives time for adaptive immunity to develop
Body is overwhelmed without an initial innate response
Need innate to adapt as innate can deal with certain smaller infections but as soon as a bigger one comes along body is overwhelmed
Functions of innate immunity?
Sense and respond to danger signals
Always on for instant response
Communicate danger to other cells of innate and adaptive immunity
Recruit immune cells to infection site (inflammation)
Tell adaptive cells when to respond
Has cellular and biochemical killing mechanisms
Innate killing mechanisms?
Phagocytosis (macrophage, neutrophil)
Secretion of cytotoxic granules (Eosinophils, neutrophils, mast cells)
Complement proteins (NK cells)
Why does adaptive take time
Need to identify and expand T and B cells that recognise the pathogen
Functions of adaptive immuntiy?
Helper T cell (Th): talk to other cells, coordinate immune responses, amplify innate immunity
Regulatory T cell (Treg): Turn off immune responses, prevent activation when not needed (allergy, infection over)
Cytotoxic T cells (CTL): kill infected cells
Antibody function?
Neutralise pathogen molecules (toxins)
Mark pathogens for destruction
Link innate and adaptive killing mechanisms
Adaptive memory response properties?
Specific to original pathogen
When that pathogen infects again response is faster and bigger as recognition of pathogen is still there
Combines speed and specificity
How do innate and adaptive work together?
Innate: detects infection, identifies its type, activates and directs adaptive response, tells whether infection still present or cleared
Adaptive: cytokines activate innate cells to amplify innate killing, antibodies work with innate cells to recognise and kill pathogens, CTLs kill infected cells
Methods of communication between cells?
Cytokines
Cell-cell communications (cell surface receptor ligand pairs)
Cytokine properties?
Many different types w different functions
Target any cell with relevant receptor allowing one cell to target many and doesn’t require cell contact
Can fire in specific direction or all around and can act locally or systemically
Cell-cell communication how?
Use receptor/ligand pairs on cell surface
Many diff receptors and ligands with diff functions
Cells need to be in contact and have correct receptor/ligand pairs
Allows precise communication between individual cells
Lymph node and spleen properties?
Specialised sites where immune responses are coordinated
Focal points for immune cell communication
Play very important role in initiation of adaptive immune responses
IBD cause?
Overzealous response against commensals
