8.2 Innate immunity Flashcards
Describe innate immunity.
The body’s first line of defence against pathogens.
- Non-specific
- Rapid response
- No prior exposure to pathogen required
- Consistency in response
- Includes natural barriers, phagocytes, soluble mediators, pattern recognition molecules
Describe the timings of each immune response after being exposed to a pathogen.
0-4 hours: Innate immunity, non-sepcific, uses pattern recognition receptors.
4-96 hours: Early induced innate response, recognition of microbial-associated molecular proteins.
96+ hours: Adaptive immune response, antigen transported to lymphoid organs and recognised by T and B cells.
Give examples of mechanical barries to infection.
- Epithelial cells joined by tight junctions
- Nasal cilia
- Movement of mucous by cilia in the respiratory tract
- Tears
- Longitudinal flow of air or fluid
Give examples of chemical barries to infection.
- Lysozyme in tears and saliva
- Low pH of gut
- Enzymes in the gut
- Fatty acids on the skin
- Antibacterial peptides
Give examples of microbiological barries to infection.
The normal flora of the skin and gut.
What barriers to infection exist in the respiratory tract?
- Nasal hairs
- Saliva (lysozyme)
- Cough/sneeze reflex
- Mucous traps microbes
- Ciliated epithelium
- Mucociliary escalator
- Alveolar macrophages
- Epithelial cells secrete chemokines to recruit neutrophils to site of infection
What barriers to infection exist in the GI tract?
- Lysozyme in saliva
- Stomach acid
- Enzymes
- Bile
- Peristalsis
- Epithelial barrier
- Bacterial flora
- Mucus and defensins
Name 7 cell types involved in innate immunity.
- Monocytes/macrophages (monocytes are phagocytic, macrophages are phagocytotic and APCs)
- Dendritic cells (important link with adaptive immunity, antigen presenting cell)
- Neutrophils (professional phagocytes)
- Eosinophils
- Mast cells
- Basophils
Innate immune cells are of what lineage?
Myeloid lineage
What is the main role of the innate immune response?
To rapidly neutralise or remove pathogens.
In what 2 ways does the innate immune response neutralise/remove pathogens?
- Phagocytosis: breakdown of pathogens
- Inflammation: allows removal of neutrophils, inflammatory mediators are released, stimulate cells locally and recruit cells to the sire of infection, affect permeability of BVs e.g. fenestrated capillaries
How do phagocytic cells recognise microbes?
- Phagocytic cells have receptors, when these bind with a ligand phagocytosis and/or inflammatory responses are induceed
What 2 types of receptors do phagocytic cells have?
- Toll like receptors (TLR2, TLR4): lead to production of inflammatory mediators
- Macrophage mannose receptor: leads to phagocytosis
Define phagocytosis.
The recognition, engulfment or and processing of pathogens and senescent cells.
Not just about infection, very important in homeostasis.
Describe the process of phagocytosis.
- Ingestion of microbe by phagocyte, transported in a vesicle = phagosome
- Phagosome fuses with lysosome = phagolysosome
- Digestion of ingested microbe by enzymes
- Dishcarge of waste materials from the cell
Describe the basic principles of inflammation.
- Occurs in response to the presence of foreign particles or microbes
- Inflammatory mediators are synthesised and released from macrophages e.g. cytokines, chemokines, lipid inflammatory mediators
- Vasodilation and increased vascular permeability cause redness, heat, pain and swelling
- Inflammatory cells migrate to the tissue to help to remove the microbe (chemotaxis and diapedesis)
What are the 3 pathways which can lead to complement activation?
- Classical pathway (adaptive)
- MB lectin pathway (innate)
- Alternative pathway (innate)
