1. Host Defences Flashcards
What is a disease?
The result of a host interaction with a pathogen
Is disease a rare or common outcome of host-pathogen interaction?
Very rare
What 3 factors are taken into account for disease?
Host (human), pathogen (bacterium), environment/circumstances
Examples of ways the host can interact with the pathogen
Vectors (insects), food, sexually transmitted
If a pathogen affects a host, it is more virulent if…
it is transmitted to the host directly
What is responsible for 70-80% of infections?
Zoonosis
What must be overcome in order for disease to occur?
Host defences
What part of the immune system is responsible for non-specific defence mechanisms?
Innate
What part of the immune system is responsible for specific defence mechanisms?
Adaptive
What is the first line of the defence (innate)?
Constitutive - skin, mucous membrane, secretions of skin & mucous membrane
What is the second line of defence (innate)?
Inducible - phagocytosis, antimicrobial proteins, inflammatory response
What is the third line of defence (adaptive)?
Lymphocytes, antibodies
The innate immune system deals with __ infections.
Acute
The adaptive immune system deals with…
Reinfection
What are constitutive defences?
- Provide general protection against invasion by normal flora, or colonisation/infection/infectious disease caused by pathogens
- “Natural Resistance”
- Always on
- Skin, mucosal surfaces, tears, saliva, sweat, urine, stomach acid etc.
- Non - specific
What are inducible defences?
- Must be induced by host exposure to a pathogen
- Only triggered after host is appropriately exposed to pathogen
- Immune responses
- Usually specifically directed against an invading pathogen
- Can be part of innate or acquired immune system e.g. cytokines, antibodies
What are the 4 components of the constitutive defences?
- Anatomical defences
- Microbial antagonism
- Phagocytosis
- Tissue bactericides (incl. complement)
What are the conditions of the skin that bacteria do not like?
- Dry
- Acidic (pH 5.0)
- Low temperature
Are resident microflora in the skin mainly Gram positive or negative?
Positive
What connects the skin to the immune system of the host?
SALT = skin associated lymphoid tissue
Where in the body would you find mucous membranes?
GIT, respiratory tract, urogenital tract
What is the main function of epithelial cells?
Absorption of nutrients
What are ‘M’ cells?
Naturally phagocytic specialised epithelial cells that are continuously sampling the bacterial population in gut & transferring that info to immune cells
Why do many pathogens target M cells?
Because they know they will get across the gut barrier naturally