Innate Immunity Flashcards
What are the three phases of response to initial infection? when do they occur?
Innate Immunity; this occurs immediately (0-4hrs) as components are already formed.
Early induced response; Early (4-96hrs) involves the recruitment of cells
Adaptive immune response (96+hrs) involves making new immune cells and antibodies
What are some mucosal surfaces where pathogens can enter?
Airway, GI tract and Gu
Name a pathogen that enters via the airway and what disease it causes?
Influenza Virus causing influenza
Name a pathogen that enters the GI tract and what disease it causes?
Salmonella causing typhoid fever
Name a pathogen that enters through the GU and what disease it causes?
Treponoma Pallidum causing syphilis
Name the ways in which pathogens can enter through external epithelia
External surface, wounds and abrasions, and insects bites
Name a pathogen that enters through external surface of epithelium and the disease it causes?
Tinea Pedis causing Athlete’s foot
Name a pathogen that enters through wounds and abrasions and the disease it causes
Clostridium tetani causing tetanus
Name a pathogen that enters via inset bites and the disease it causes
Plasmodium causing malaria
What are the different barriers to infection and name some specific examples
Mechanical - movement of cilia and tight junctions between cells
Chemical - Fatty acids on skin & Stomach acid.
Microbiological - Normal flora to compete for nutrients and attachment
One pathogen crosses epithelial barrier what occurs? And what is this enhanced by?
It is recognised and ingested by mono-nuclear phagocytes or macrophages. This is enhanced by the presence of receptor on the phagocytic cell that can recognise pathogens
Name some of the bacericidal effects and agents produced by phagocytes
- Acidification (acidic environment)
- Toxic oxygen derived products
- Toxic nitrogen oxides
- Peptides (defensins)
- Enzymes (lysosmye)
- Competitors (lactoferrin)
All cells of the immune system are derived from what?
Haemotopoeitic stem cell
What is key about the circulation time of neutrophils
They only circulate for 12 hours. So if a drug or agent is affecting the immune system this is first seen here.
What do mast cells release?
Substances that effect vascular substances. They are full of histamine
What is the function of B and T cells
B cells - Production of antibodies
T cells - Become cytotoxic T cells (CD8) or helper T cells (CD4)
What are neutrophils, basophils and eosinophils involved in?
Neutrophil - Ingest bacteria
Eosinophil - Important in parasite defence
Basophils - Involved in hypersensitivity reactions
What is the role of natural killer cells and dendritic cells?
Natural Killer - Recognise virally infected cells
Dendritic cells - Bridges innate and adaptive immune responses (antigen presenting cells)
What do virally infected cells release?
Interferon alpha (IFN-α) and Interferon Beta (IFN-β)
What does the release of IFN-β and IFN-α cause?
Near by cells to become slightly more resistant to the virus, upregulates a class of proteins called MHC class 1 and finally activates other natural killer cells.
Describe what Natural Killers cells interact with and what happens when the cell is infected?
They interact with MHC class 1 receptors on healthy cells and this stops the NK from killing it. However when a cell is infected with a virus it no longer produced MHC class 1 receptors so the NK cannot interact and therefore it kills the cell
What are two of the main complement pathways and what activates them?
Classical Pathway - Antibody binds to specific antigen on pathogen surface
Alternative Pathway - Pathogen surface creates local environment which triggers complement activation
What are some of the outcomes for the complement system?
- Recruitment of cells
- Opsonization of pathogens
- Lysis and death of pathogens
Name an example of an opsonin
C3b
Name two examples of mediators of inflammation
C5a and C3a
What is the classical pathway initiated by?
Activation of the c1 complex which binds to antigens on the pathogen surface.
What occurs tp C3 in the complement cascade?
It is cleaved into C3b which sticks to the cell acting as an opsonin and C3a floats away and recruits more cells.
What is the alternative pathway caused by?
The spontaneous hydrolysis of serum C3. C3b then binds to pathogen surface creating that environment which triggers the alternative pathway.
What forms the membrane attack complex (MAC) and what does it do
It is formed from complement serum proteins; C6, C7, C8, and C9 and it punches wholes in the surface of pathogens causing it to die
What is the function of CD59?
It prevents membrane attack complexes from forming on the surface of host cells. SO it is there for protection
Name some examples that inhibit the complement system and why this is needed
DAF, MCP and Cr1. This is to prevent immune responses when they are not needed.
Patients with complement Deficiencies often present with what?
Recurring bacterial infections which differ depending on which complement serum protein they are deficient in.
