Lecture 4- Innate Immunity Flashcards
What is the infection model?
That pathogen with its virulence factors combine with patient to give an infection which is then managed and an outcome achieved
Corticosteroids use?
Reduce inflammation
Immune system?
Cells and organs responsible for the body’s immune defences against infectious and non-infectious conditions
What is an infectious disease?
When the pathogen succeeds in evading or overwhelming the hosts immune defense
What are the roles of the immune system?
To recognise pathogens
To contain or eliminate them
To minimise damage to the host
To remember the pathogen for the future
Adaptive vs innate immunity?
Innate is non specific, recognises groups of microbes. Is fast acting and, lacks memory, no change in intensity
Adaptive immunity is long lasting. Slow to react but can target microbes specifically. Has memory and can change intensity
What are the four innate immunity barriers?
Biological
Physical
Physiological
Chemical
Physical barriers of innate immunity?
Skin
Mucous membranes
Bronchial cilia (cyclic fibrosis sufferers more prone to infection)
Physiological innate immunity barriers?
Coughing
Sneezing
Vomiting
Diarrhoea
Chemical barriers?
Low pH
Antimicrobial molecules such as gastric acid, lysozymes and mucus
Biological barriers?
Normal flora- non pathogenic microbes that inhabit the mouth, vagina and GI tract etc and prevent growth of abnormal pathogens
Absent in internal organs and tissues
Produce antimicrobial chemicals, vitamins like K and B12 and compete with pathogens for resources
What is the problem with biological barriers?
If they end up in the wrong lace or are allowed to multiply significantly they can damage the host
Where should you never see biological flora?
In internal organs or tissues
Given an example of normal flora of the skin that can cause problems?
Staphylococcus aureus which causes cellulitis
How can flora be displaced and cause problems?
Break in skin such as IV line or surgery
Faecal oral route eg salmonella
Faecal urethral rough eg UTI from E. coli
Poor dental hygiene or dental work
What patients are high risk for serious infections?
Asplenic and hyposplenic
Patients with prosthetic valves (endocarditis)
Patients who had endocarditis previously
When can normal flora become a problem?
When it overgrows due to host being immunosuppressive eg AIDS and diabetes
When normal flora is depleted due to antibiotics eg thrush (candida albicans takes over)
Anti acids lower stomach pH
What two branches are there of innate immunity?
Those that prevent pathogens entering:
Biological
Chemical
Physical
Physiological
Those that contain and eliminate pathogens once they have entered:
phagocytes
Chemicals
What are the two types of microbes that can enter the body?
Exogenous and endogenous
What are the main phagocytes?
Macrophages- all organs
Neutrophils- recruited by chemokines
Monocytes- recruited to infection site and differentiate into macrophages
Cytokines vs chemokines?
Cytokines are signalling molecules and chemokines are a type of cytokine that causes cells to be recruited to an infection site
Basophils and mast cells?
Early indicators of inflammation and important in allergic reactions
Eosinophils?
Defence against parasites (worms)
Natural killer cells?
Kill all abnormal host cells, virus infected or malignant
Dendritic cells
Present microbial antigens to T cells (acquired immunity)
Mast cells?
Similar to basophils, responsible for anaphylaxis
How are pathogens recognised?
Through PAMPs and PRRs.
PAMPs= pathogen associated recognition patterns
PRRs= Pathogen recognition receptors which sense PAMPs
What is opsonisation of pathogens?
Coated with proteins called opsonins that bind to the microbial surface and enhance attachment of phagocytes
What is opsonisation essential for?
Clearing encapsulated bacteria such as neisseria meningitidis and streptococcus pneumoniae
Phagocytosis process?
Chemotaxis brings phagocyte to microbe.
Microbe is recognised and adhered to. Microbe is phagocytosed. A phagosome is formed which is combined with a lysosome which degrades the microbe. Residual bodies are then exocytosed
How do phagocytes kill?
Oxygen dependant pathway= respiratory burst
Oxygen independent pathway= lysozyme and proteolytic enzymes
What are the chemicals involved in the second line of defence of innate immunity?
Complement system and cytokines
What can the complement system do?
Recruit phagocytes through cytokines
Kill pathogens through punching holes in their membranes
Opsonisation of pathogens
What can cytokines do in an immune response?
Cause neutrophil mobilisation. Increase body temperature through the hypothalamus. Cause vasodilation and increase vascular permeability
Complement system function?
To help antibodies and phagocytes clear microbes. Also promotes inflammation
Important proteins of complement system?
C3a and c5arecruit phagocytes through chemotaxis
C3b and c4b opsonise pathogens
C5-c9 kill pathogens
Actions of macrophage derived cytokines?
TNF alpha, IL-1 and IL-6
Act systemically on liver to produce CRP, bone marrow to increase neutrophil mobilisation and hypothalamus to increase body temperature
Local inflammatory actions such as vasodilation and vascular permeability
