15. IMMUNE SYSTEM Flashcards
Describe the key differences between ‘innate immunity’ and ‘specific/adaptive immunity’
Innate immunity provides a broad, non-specific immune response to any foreign substances and/or pathogens. This includes the physical barrier such as the skin and the mucous membranes, as well as some immune cells, proteins and processes such as fever and inflammation.
In specific immunity a response is produced against a specific pathogen only
List four ways in which pathogens can enter the body
Through a break in the skin Through the respiratory system Through the digestive system Through the reproductive system Through the eyes
Define the following terms:
a. Antigens
b. Antibodies
a. An antigen is a substance (usually a protein molecule) that can be recognised by leukocytes and helps them to discern whether a cell is own or foreign
b. Antibodies are proteins that are produced in response to a specific antigen and combines with it
List five components of the first line of immune defence
Skin, sweat, sebum, mucous, mucociliary escalator, macroscopic nasal hairs, saliva, tears, gastric acid, vomiting, diarrhoea
Explain what is meant by a ‘self-antigen’.
An antigen present on the cell membranes of the body’s own cells which identifies it to leukocytes.
How does the micro ciliary escalator contribute to immune defence?
The cilia in the mucus membranes of the respiratory tract propels foreign particles towards the pharynx where they can be swallowed or coughed up.
How do the following contribute to immune defence:
a. Microflora
b. Gastric acid
c. Vagina
a. Microflora generally outcompete pathogens for attachment sites on epithelial cell surfaces
b. The acidity of gastric acid destroys many bacteria.
c. The vagina is acidic, making it unfavourable for microbes to inhabit.
Describe the role of transferrins
Transferrins are iron-binding proteins in blood which act to inhibit the growth of certain bacteria, by reducing the amount of available iron (which bacteria could use for their growth).
List three ways in which the complement system destroys microbes
- By promoting phagocytosis: the fragment C3b ‘coats’ microbes in a process called ‘opsonisation’ which promotes the attachment of a phagocyte to the microbe.
- Contributes to inflammation: C3a and C5a bind to mast cells and cause them to release histamine.
- Causes cytolysis by destroying microbes
Describe the role of the following cytokines:
- Interleukin-1
- Tumour Necrosis Factor (TNF)
- Interleukins act as mediators between leukocytes. Interleukin-1 is produced by macrophages and one of its key functions is to induce fever.
- TNF promotes the accumulation of neutrophils and macrophages and causes cell death.
Describe the working of interferons in viral replication
Interferons are proteins that are produced by virus-infected cells. They diffuse to uninfected neighbouring cells and interfere with the viral replication process within these cells, halting the spread.
Name two phagocytic cells
Neutrophils
Macrophages
Explain the difference between ‘fixed’ and ‘wandering’ macrophages?
Wandering macrophages are monocytes that migrates to sites of infection and enlarge.
Fixed macrophages stand guard in specific tissues and do not move.
Name three locations of fixed macrophages
Kupffer cells in the liver Alveolar macrophages in the lungs Langerhans cells in the skin Histiocytes in connective tissue Microglia in nervous tissue
Describe in detail the five stages of phagocytosis
- Chemotaxis: Chemicals released by microbes, leukocytes, damaged tissue and activated complement system attracts phagocytes.
- Adherence: Attachment of phagocytes to the target (aided by complement)
- Ingestion: The cell membrane extends projections to engulf the microbe.
- Digestion: The ingested structure merges with lysosomes to form phagolysosomes and lysozymes digest it.
- Excretion: Indigestible material is excreted.
Describe specifically how Natural Killer cells cause cytolysis.
Natural Killer cells are lymphocytes that present in the blood, lymph nodes, spleen and bone marrow that attack anything they do not recognise. They bind to their target cell, release granules containing the protein ‘perforin’ which inserts into that cell’s membrane and creates a channel for tissue fluid to flow into the cell, causing it to burst.
List two factors that can trigger inflammation
Pathogens Physical trauma (abrasions, wounds, breaks) Chemicals Extreme temperatures Cell distortion or disturbance
Name five cardinal signs of inflammation
Heat Redness Swelling Pain Loss of function
List two benefits of inflammation
- Inflammation promotes phagocytosis (increase in temperature promotes chemotaxis etc.)
- Promotes immune response: vasodilation, increased permeability allows cells and proteins to leave the blood and enter the affected site.
- Dilutes toxins
- Fibrin formation: affected area is isolated
List two harmful effects of inflammation
- Swelling: can be dangerous if in the cranium
- Pain: can become chronic
- Adhesions and scar tissue
- Atherosclerosis: Inflammation is a key feature
Describe in detail the three stages of inflammation
- Vasodilation and increased permeability: Allows additional blood, oxygen, nutrients, immune cells and repair substances to the area. More removal of toxins and dead cells. Redness, swelling and heat results and pain is due to injury to neurons and toxins released by microbes.
- Emigration of phagocytes: Chemotaxis causes phagocytes to migrate to the scene
- Tissue repair
Discuss the function and release site of the following inflammatory mediators:
- Histamine
- Leukotrienes
- Kinins
- Prostaglandins
- Histamine is released by mast cells and basophils and causes vasodilation and increased permeability.
- Leukotrienes are released by mast cells and basophils and they attract phagocytes and increase vessel permeability.
- Kinins are peptides that are released in the blood which induce vasodilation and increased permeability. They attract phagocytes and interact with prostaglandins to induce pain.
- Prostaglandins: Lipids released by damaged cells which enhance the effects of histamine and kinins.
List two functions of non-specific fever
- Makes interferons more effective
- Inhibits the growth of some microbes
- Speeds up the reactions that aid repair
Name the cytokine that induces fever
Interleukin-1