Immune System Flashcards
What is the immune system?
A versatile defence system that protects us from diseases caused by pathogenic microbes
How many lines of defence do we have?
3
Which lines of defence protect us from anything (non-specific) foreign coming into our bodies?
First and second line
Describe the first line of defence.
A physical barrier against foreign bodies and microbes, created by the skin and mucous membranes
What does innate mean?
Inborn / natural
Describe the third line of defence.
The advanced part of our immune system, which targets SPECIFIC foreign bodies
Describe the second line of defence.
A non-specific immune response, which includes some immune cells, proteins, fever and inflammation.
Which line of defence targets specific foreign bodies?
The third line
Which lines of defence target non-specific foreign bodies?
First and second line
Which lines of defence make up our innate immunity?
First and second line
A fever is part of which line of defence?
The second
What is the purpose of a fever?
To create an unfavourable environment for most pathogens (too hot).
What is the purpose of inflammation?
To create an unfavourable environment for most pathogens.
List 3 signs/symptoms of inflammation
Redness, pain, swelling
List 2 things that can cause inflammation.
- Localised physical trauma
2. An infectious pathogen, trying to cause disease/damage.
Why is inflammation part of the second line of defence?
Because it is non-specific, and targets anything that is foreign.
Which line of defence is known as specific / adaptive immunity?
The 3rd line of defence
In which line of defence are memory cells created, in order to protect us from specific pathogens?
The 3rd line of defence
Why can we often get infected with a particular virus more than once?
Because viruses mutate (i.e, the flu).
Name 1 virus that frequently mutates
Influenza (flu)
What is a pathogen?
An infectious organism that can cause disease in a host
List 4 ways in which infectious organisms / pathogens can get into the body
- Through breaks in the skin (i.e, a cut)
- Via inhalation
- Via swallowing
- Via the eyes
How does the digestive system provide first line defence against pathogens?
- Saliva contains antibodies
- Stomach acid provides a very unfavourable environment to most pathogens (but not if stomach acid is low)
Name 1 thing that can cause reduced stomach acid and reduced salivary antibodies, in turn causing reduced immunity.
Stress
What is an antigen?
A cell marker (usually protein) that can be recognised by leukocytes.
How many types of antigen are there?
2
Name the 2 types of antigen
- Foreign antigens
2. Self antigens
Where would you find self-antigens?
On cell membranes (self antigens are cell membrane proteins)
Where would you find foreign antigens?
On microbes, bacteria, viruses, food, or drugs
What are antibodies?
Proteins produced in response to a specific antigen
Self antigens are produced through protein synthesis (transcription, translation and then embedding into cell membrane). True or false?
True
Which process are ‘transcription’ and ‘translation’ a part of?
Protein synthesis
What are foreign antigens?
Antigens not made by the body (i.e a bacteria or virus)
An immune response is created when ______ and ______ join together.
Antigens and antibodies
The ______ and _______ ________ are the first line of defence against pathogens.
Skin and mucous membranes
The skin acts as a physical barrier with its layers of tightly packed ________ cells.
Epithelial
How does the shedding of the epidermis layer of the skin contribute to our immune function?
When the epidermis sheds it also sheds any microbes that are on it.
How often is the epidermis of the skin entirely replaced?
Every 40 days
List 2 ways in which sweat contributes to immune function?
- It removes microbes from the surface of the skin
2. It contains IgA antibodies
Where would you find IgA antibodies?
Sweat, saliva, tears, breast milk
IgA = first letter of alphabet, first line of defence
What does Ig stand for?
Immunoglobulin
Immunoglobulins are antibodies. True or false?
True
What type of antibodies are found in sweat, saliva, tears, mucous secretions and breast milk?
IgA
How does sebum contribute to immune function?
It contains fatty acids which inhibit microbial growth (stop bacteria from undergoing mitosis).
List 3 places we find mucous membranes.
- The digestive tract
- The respiratory tract
- The urogenital tract
Saliva, tears and mucous secretions wash away microbes, and also contain anti- ________ substances.
Anti microbial
Name 2 body fluids that contain IgA and lysozymes
Tears and saliva
What are lysozymes?
Enzymes that break down bacterial cell walls
Where would you find the mucocilliary escalator?
In the respiratory tract
Tears are really important to provide an immune function on the surface of the eye. True or false?
True
Name 2 mucous secretions (substances secreted by mucous membranes).
Tears and saliva
What does the Ig in IgA / IgE / IgB, etc stand for?
Immunoglobulin
What is secretory IgA and how can it be measured?
Secretory IgA is the IgA present in the stool.
It can be measured via very comprehensive stool testing.
Why can IgA levels be used as an indicator of stress in a patient?
Because higher stress = lower IgA.
The more stressed a person is, the lower their IgA levels (and therefore general immune function) will be.
Vomiting and diarrhoea are rapid means of expelling _______.
Pathogens
Microflora generally outcompete pathogens for attachment sites on epithelial cell surfaces (the car parking spaces analogy), but where in the body / on which epithelial cell surfaces are they generally found?
In the large intestine
small intestine also, if SIBO is present
What is GALT?
Gut Associated Lymphoid Tissue
70% of our immune system is in the ______, in the form of _____
In the gut.
In the form of GALT (Gut Associated Lymphoid Tissue)
Which line of defence includes:
Complement System, Transferrins, Phagocytes, Natural Killer Cells, Inflammation, Cytokines and Fever?
2nd line of defence
List 4 mediators / factors in the second line of defence.
- Complement system
- Transferrins
- Phagocytes
- Natural Killer Cells
- Inflammation
- Cytokines
- Fever
What is the Complement System?
A series of proteins
List 2 outcomes produced by the complement system.
- Inflammation
2. Phagocytosis
What are transferrins?
Iron-binding proteins
Where are transferrins found?
In haemoglobin (Hb), in the blood. They are part of the Hb structure.
What do transferrins do?
They latch on to iron molecules and lock it away, stopping bacteria/pathogens stealing the iron for their own energy.
What are phagocytes?
White blood cells that specialise in engulfing / eating.
What are Natural Killer Cells?
Immune cells that release a protein called Perforin, which spears foreign cells, causing damage to the membrane and allowing water in, which in turn causes the foreign cell to rupture.
What is perforin?
A protein released by Natural Killer Cells
What do Natural Killer Cells do to foreign cells / pathogens?
They go around stabbing them and causing them to rupture! (Using the protein ‘perforin’)
Why is inflammation important?
Because it helps to attract white blood cells to the area (it’s a warning sign - a bit like pushing a fire alarm)
What are cytokines?
Messenger proteins that are released by cells
think of them as text messages to other cells
Which supplement can feed bacterial growth if not carefully controlled/monitored?
Iron
In adults, each Hb molecule contains ___ polypeptide chains; 2 x alpha and ___ x _____
4
2 x alpha, 2 x beta
How many polypeptide chains does 1 haemoglobin molecule have?
4
How many iron molecules can each haemoglobin carry?
4 (1 per polypeptide chain)
What is the complement system?
A defence system (involving cascade of events) made of over 30 proteins produced by the liver.
Where are the complement system proteins manufactured?
In the liver
Complement proteins are inactive and only become active when split into active fragments by ______
Enzymes
The main complement protein is known as ____.
C3
Whenever you see a letter after a complement protein (i.e, C3a and C3b), it means that protein is fragmented and active. True or false?
True
The most common way in which the complement cascade is activated is through the classical ________.
Pathway
What does the ‘classical pathway’ of the complement cascade involve?
An antigen and an antibody joining together
antigen-antibody complex
Give an example of a pathology that involves the classical pathway of the complement system.
Glomerulonephritis
(antigen-antibody complexes deposit on the kidney nephrons, causing inflammation and local damage, and subsequently loss of proteins into urine)
What is opsonisation?
The coating of a microbe with an identification protein
Collectively, complement proteins destroy microbes by:
- Promoting __________
- Contributing to ________
- Causing _______
- Phagocytosis
- Inflammation
- Cytolysis
How do complement proteins promote phagocytosis?
C3b fragments coat microbes in a protein (‘opsonisation’), which allows them to be identified as foreign by phagocytes and then engulfed.
In the complement system (second line of defence), complement protein fragments contribute to inflammation by binding to _____ cells and cause them to release ______
Mast Cells
Histamine
What is cytolysis?
Destroying (bursting) microbes
Which small protein hormones act as chemical messengers between different types of cells?
Cytokines
Cytokines are secreted by _________.
Leukocytes
What is the name given to the group of non-antibody proteins secreted by leukocytes?
Cytokines
Cytokines act on cells involved in _____
Immunity
Name 3 types of cytokines.
- Interleukins
- Interferons
- Tumour Necrosis Factor (TNF)
Interleukins are a type of _______
Cytokine
Interferons are a type of _____
Cytokine (Anti-viral proteins)
Which type of cytokine acts as a mediator between leukocytes?
Interleukins
Interleukins (cytokines) are mostly produced by ___-_____ cells.
T-Helper cells
Interleukin 1 (cytokine) is released by _______
Macrophages
Interleukin 1 (cytokine) is a protein hormone that tells your brain to ______ body temperature.
Increase
Interferons (cytokines) are involved in anti-_____ responses.
Anti-viral
Cells that are infected by a virus produce this type of cytokine.
Interferons
Which type of cytokine tells all surrounding cells to stop dividing, in an effort to stop viral spread/infection?
Interferons
Can viruses undergo mitosis themselves?
No. They can only replicate once they get inside one of our host cells.
Which type of pathogen can only replicate using host somatic cells?
Viruses
Tumour necrosis factor is a cytokine protein that promotes the accumulation of which 2 types of white blood cell?
Neutrophils and macrophages
In which line of defence would you find interferons and interleukins?
The second line of defence (these are both cytokines - protein chemical messengers)
Anti-viral proteins (cytokines) are called _____.
Interferons
Which WBC’s carry out phagocytosis?
Phagocytes
What is the name of the process whereby we engulf and digest cells / microbes?
Phagocytosis
Name 2 types of phagocytes.
Neutrophils
Macrophages
Which type of phagocytic cell is always first on the scene?
Neutrophils
Macrophages are found in ________, whereas monocytes are found in ________ (they are the same thing, other than location).
Macrophages = tissue Monocytes = blood
Monocytes travel in the blood, and when they arrive at a tissue they transform into _______
Macrophages
Phagocytes are non-selective in their targets. What does this mean?
They attack and engulf anything with a foreign antigen.
What do phagocytes use to break down foreign cells?
Lysozomes (balls of digestive enzymes)
Macrophages are antigen presenting cells. True or false?
True
Macrophages present parts of foreign cells they’ve digested to __ - ________.
T-lymphocytes
Name 2 types of antigen presenting white blood cells.
- Macrophages
2. B-lymphocytes
Which WBC’s do macrophages and B-lymphocytes present antigens from broken down foreign cells to?
T-lymphocytes
Macrophages are known as either _______ macrophages, or ______ macrophages.
Wandering or fixed
What is the difference between wandering and fixed macrophages?
Wandering macrophages are monocytes that have migrated in the blood to a site of infection and enlarged in the tissue.
Fixed macrophages stand guard in specific tissues and do not migrate.
Give 3 examples of where you would find fixed macrophages.
- Kupffer cells in the liver
- Alveolar macrophages in the lungs
- Microglia in the central nervous system
Explain the process of phagocytosis in 5 steps.
> Chemotaxis (attracts phagocytes to the area).
Adherence of phagocyte to target
Ingestion of the microbe
Digestion of the microbe, via lysosomes
Excretion of indigestible material
Phagocytosis occurs in ___ stages.
5 stages
What is chemotaxis?
Chemical attraction.
The release of chemicals by microbes, leukocytes, damaged tissue and activated complement proteins.
Name a bacteria that is resistant to the adherence part of phagocytosis, and therefore cannot be digested as normal.
Tuberculosis
A macrophage is an ______ presenting cell.
Antigen
Which non-specific lymphocytes account for just 5 - 10% of lymphocytes?
Natural killer cells
List 4 places that natural killer cells are found.
- Blood (predominantly)
- Lymph nodes
- Spleen
- Bone Marrow
Natural Killer Cells (NKC) attack anything they do not recognise. Name one type of abnormal body cell (not foreign cell) that they may attack.
Cancerous cells
Cancerous body cells will display abnormal surface antigens. True or false?
True
Natural Killer (NK) cells bind to a target cell and release _______ containing the protein ‘______’.
Granules, containing perforin
How does perforin cause cytolysis in a foreign or abnormal body cell?
Perforin inserts into the cell membrane and creates a channel for tissue fluid to flow into the cell. This causes the cell to rupture.
List the 5 cardinal (typical) signs of inflammation.
1. Redness 2, Heat 3. Pain 4. Swelling 5. Loss of function
Mast cells release _______ and _______
Histamine and heparin
_______ is the key chemical in inflammation and is created by the de-granulation of Mast cells.
Histamine
Describe the 3 basic stages of inflammation.
- VASODILATION (increased blood flow)
- Increased vascular permeability (allows arrival of immune cells, antibodies and clotting factors)
- Redness, swelling and heat
- EMIGRATION OF PHAGOCYTES (via chemotaxis) - neutrophils and monocytes
- TISSUE REPAIR
How many clotting factors are there?
13
Which cells release histamine?
Mast cells and basophils
Which chemical mediator, involved in inflammation, causes vasodilation and increased permeability?
Histamine
List 4 inflammatory mediators
- Histamine
- Leukotrienes
- Kinins
- Prostaglandins
Leukotrienes (inflammatory mediator) are produced by ________ and ____ _____
Basophils and Mast cells
What do leukotrienes do?
Attract phagocytes and increase blood vessel permeability, as part of the inflammatory response.