S3) Innate Immune System Flashcards
What is the immune system?
The immune system is a network of cells and organs that contribute to immune defences against infectious and non-infectious conditions (self vs non-self)
Identify 4 roles of the immune system
- Pathogen recognition: cell surface and soluble receptors
- Containing/eliminating the infection: killing and clearance mechanisms
- Regulating itself: minimum damage to host (resolution)
- Remembering pathogens: preventing disease from recurring
Compare and contrast the innate and adaptive immunity
- Innate (immediate protection): fast (seconds), lack of specificity and memory, no change in intensity
- Adaptive (long lasting protection): slow (days), specificity, immunologic memory, changes in intensity
What is an infectious disease?
An infectious disease is when a pathogen succeeds in evading and/or overwhelming the host’s immune defences
Identify and describe the 3 mechanisms by which micro-organisms trigger the inflammatory cascade
- Pilus enhances attachment
- Lipopolysaccharide endotoxins triggers inflammation
- Polysaccharide capsule promotes adherence and prevents phagocytosis
The inflammatory cascade is triggered when an endotoxin binds to macrophages.
Outline its following phases:
- Local
- Systemic
- Sepsis
- Local: cytokines, TNFs and interleukins promote wound repair and recruit the reticuloendothelial system
- Systemic: cytokines released into circulation and stimulate GF, macrophages & platelets (aims to control infection)
- Sepsis: cytokines lead to activation of humoral cascades, RE System, circulatory insult (infection is not controlled)
Explain the relationship between sepsis and coagulation
- Cytokines released in sepsis initiates production of thrombin
- Thrombin promotes coagulation and cytokines also inhibit fibrinolysis
- Coagulation cascade leads to microvascular thrombosis → organ ischaemia, dysfunction and failure (sepsis)
What are the three factors determining the outcome of the host-pathogen relationship?
- Infectivity
- Host’s immune response
- Virulence
The first line of defence consists of factors that prevent entry and limit growth of pathogens.
Identify the different innate barriers to infection
- Physical barriers
- Physiological barriers
- Chemical barriers
- Biological barriers
Identify the 3 different physical barriers to infection in the innate immune system
- Skin
- Mucous membranes: mouth, resp tract, GI tract, urinary tract
- Bronchial cilia
Identify and describe the 4 physiological barriers to infection in the innate immune system
- Diarrhoea – food poisoning
- Coughing – pneumonia
- Sneezing – sinusitis
- Vomiting – food poisoning, hepatitis, meningitis
Identify and describe the 2 different chemical barriers to infection in the innate immune system
- Low pH – skin (5.5), stomach (1-3), vagina (4.4)
- Antimicrobial molecules:
I. IgA (tears, saliva, mucous membranes)
II. Lysozyme (sebum, perspiration, urine)
III. Mucus (mucous membranes)
IV. Gastric acid + pepsin
Identify and describe the biological barrier to infection in the innate immune system
Normal flora:
- Non pathogenic microbes
- Found in nasopharyngeal, mouth/throat, skin, GI tract, vagina
- Absent in internal organs/tissues
What are the benefits of normal flora as a biological barrier in the innate immune system?
- Compete with pathogens for attachment sites and resources
- Produce antimicrobial chemicals
- Synthesise vitamins (K, B12, other B vitamins)
Describe how the different innate barriers work together to maximise the response against microbes
Innate barriers trigger the second lines of defence:
- Phagocytes
- Chemicals