Immune System Flashcards
Describe the key differences between the ‘innate immunity’ and the ‘specific / adaptive immunity’.
Innate immunity is inborn or natural and it is non specific. It attacks anything that our body perceives as foreign or dangerous.
Specific/adaptive immunity is activated by the innate immune system producing a response to a specific pathogen. It creates immune cells with memory against specific foreign cells.
List FOUR ways in which pathogens can enter the body.
Break in the skin
Respiratory System
Digestive System
Male/female reproductive systems
Eyes
Define the following terms:
a. Antigens
b. Antibodies
a. Antigens
A substance (usually proteins) that can be recognised by leukocytes. It acts like a marker or flag or passport.
b. Antibodies
Proteins that are produced in response to a specific antigen. They combine with these specific antigens.
When antigens and antibodies join together they create an immune response.
Explain what is meant by a ‘self-antigen’.
Any cell that is one of our own will contain lots of self antigens on the cell membrane. They say I’m safe, I’m part of you and here is the proof.
Foreign antigens are antigens that we have not produced ourselves. We find them on cells like bacteria or viruses. When a leukocyte stroll by and sees its passport it will want to get rid of it.
Describe how the following contribute to the first line of immune defence:
a. Sweat
b. Sebum
c. Saliva
d. Tears
a. Sweat;
* Sweat glands on the dermis contain antibodies called IgA
(Ig = immunoglobulin = antibody)
A = first letter of the alphabet and first layer of our body = saliva, sweat, tears, mucus secretions all have IgA
- sweat secreted onto the skin surface, contains antibacterial and antifungal substances which remove microbes from the skin
b. Sebum
* Contains fatty acids which inhibit microbial growth
c. Saliva
* Wash away food debris they may have microbes
* contain anti-microbial substances
* Contain IgA and lysozymes. Lysozymes are enzymes that break down bacterial cell walls.
d. Tears
o Wash away microbes on the surface of the eyes, and also contain anti-microbial substances.
o Contain IgA and lysozymes. Lysozymes are enzymes that break down bacterial cell walls.
Explain how the mucociliary escalator contributes to immune defence.
Cilia propel the foreign substances toward the pharynx where they are swallowed.
Describe how the following contribute to immune defence:
a. Microflora
b. Gastric acid
c. Vagina
d. Urine/faeces
e. Vomiting/diarrhoea
a. Microflora
Generally out compete pathogens for (i) the attachment sites on the epithelial cell surfaces (ii) essential nutrients
b. Gastric acid
The acidity destroys many bacteria. Very acidic at 2-3 PH.
c. Vagina
Acidic environment in menstruating women making it unfavourable for microbes to inhabit
d. Urine/faeces
Expels microbes
e. Vomiting/diarrhoea
Rapid means of expelling pathogens
Describe the role of transferrin’s.
2nd line of defence. Iron binding proteins in the blood. They latch on to iron, binding to it, shielding it and stopping bacteria from using it. Bacteria love iron and use it for growth.
Transferrins are in the blood because that is where we find iron.
List THREE ways by which the complement system destroys microbes.
- Promoting Phagocytosis:
The activated C3b fragment attaches to microbes in a process called opsonisation.
It acts as a kind of tracking device alerting incoming neutrophils and macrophages that this is the cell that needs to be attacked.
-
Contributing to inflammation
C3a and C5a bind to receptors on mast cells and cause them to release histamine. -
Causing Cytolysis
A hole is created in the microbe allowing fluid in causing the cell to swell, distend and then rupture.
What is a cytokine?
Cytokines are small protein hormones that stimulate or inhibit normal cell functions.
They are secreted by Leukocytes.
They act on cells involved with immunity
Describe the role of the following cytokines:
a. Interleukin-1
b. Tumour necrosis factor
a. Interleukin-1
Interleukins are a group of cytokines that act as mediators between leukocytes. They are really important in the immune response. Names Interleukin 1,2, 3, 4 etc.
Interleukin 1 is released by macrophages when engulfing a pathogen. It goes into the blood and travels to the brain where it tells the hypothalamus to increase body temperature. This leads to a fever.
So interleukin 1 is the messenger between the macrophage and the hypothalamus saying please increase temp.
b. Tumour necrosis factor
Protein that attracts neutrophils and macrophages to the area and can cause cell death.
Discuss the following statement:
‘Interferons stop viral replication’
Interferons are a type of cytokine (along with Interleukins and Tumour Necrosis Factor).
Interferons are antiviral proteins produced by cells that are infected by a virus. Interferons ‘interfere’ by telling all of the cells surrounding the virus to stop dividing.
The way that viruses grow is through replication inside our host cells. However they can only do this once they are inside the cell where they can integrate their own DNA and then get our cells producing their own DNA.
Therefore one of our strategies needs to be stopping the surrounding cells from dividing and thus replicating the virus.
Eg: someone comes to the door that no one wants to see. Interferons send a Whatsapp message to everyone else saying X is at the door. Keep the door shut and stay quiet until they leave.
Name TWO phagocytic cells.
The two major types of phagocytic cells are macrophages and B lymphocytes
What are Macrophages?
Antigen presenting immune cells.
Known as Monocytes in white blood cells and macrophage when they migrate from the bloodstream into any tissue in the body.
Macrophages break down the pathogen using lysozymes. Most of what is broken down is excreted but some of it will be displayed on the cell membrane of its own structure. This ‘foreign antigen’ is presented to T-Lymphocytes so that they learn about the threats in the body.
Explain the difference between ‘wandering’ and ‘fixed’ macrophages.
Wandering Macrophages are formed from monocytes that migrate to the site of infection and enlarge.
Fixed macrophages are fixed and stand guard in specific tissues.
Name THREE locations for fixed macrophages.
- Histiocytes (connective tissue macrophages).
- Kupffer cells (only in the liver).
- Alveolar macrophages (lungs).
- Microglia (nervous tissue).
- Langerhans cells (skin).
- Tissue macrophages (spleen, bone marrow, lymph nodes).
Describe in detail the FIVE stages of phagocytosis.
Hint : CAIDE
1. Chemotaxis (to attract phagocytes)
The release of chemicals by
- microbes
- leukocytes
- damaged tissue and,
- activated complement
(As soon as you damage an area of tissue or have microbes in an area or have proteins being released by leukocytes, there will be lots of triggers than attract phagocytes to the area.)
2. Adherence
Attachment of the phagocyte to the target. Phagocytes have these extensions that attach onto the foreign cell. When they attach that is known as adherence.
(Granuloma: Some microbes are resistant to adherence. TB is an example and this means that TB is resistant to the whole phagocytosis process so we have to do something different. Instead, we surround it with layers of immune cells.)
3. Ingestion
The cell membrane extends projections that engulf the microbe.
4. Digestion
The engulfed microbe merges with lysosomes that have digestive enzymes called Lysozymes which digest the microbe.
5. Excretion
Whatever is not ingested in the stage 4 is excreted. The indigestible material.
List five components of the first line of immune defence
- Skin
- Mucus membranes
- Mucociliary escalator
- Vomiting
- Diarrhoea
- Saliva
- Tears
- Sweat
- Sebum
- Nasal hairs
*
Where are the complement proteins produced? Explain the role of the complement.
Produced in the liver
Produce a cascade of immune response that leads to
- inflammation
- phagocytisis and
- cytolysis
Describe specifically how natural killer cells cause cytolysis.
Through cytolosis which is one of the three ways by which the complement system destroys microbes.
- NK cells bind to a target cell and release granules containing the protein perforin
- Perforin can be likened to a spear that perforates the foreign organism cell membrane creating a hole for tissue fluid to flow into the cell and causing it to rupture.
- Being non-specific they attack anything with a foreign antigen
List TWO factors that trigger inflammation.
- Pathogens
- Abrasions
- Chemicals
- Damage to a tissue
- Extreme temperatures.
Name THREE cardinal signs of inflammation.
- Redness
- Heat
- Pain
- Swelling
- Loss of Function
List TWO harmful effects of inflammation.
- Swelling can be dangerous, for example in the cranium leading to ICP
- Pain can become chronic
- Scar tissue and adhesions if continuous inflammation. Eg: endometriosis
- Atherosclerosis inflammation is a key feature of this process
What are the THREE stages of inflammation.
Stage 1: Vasodilation and increased permeability.
Stage 2: Emigration of phagocytes
Stage 3: Tissue Repair
What happens in the THREE stages of inflammation?
Stage 1: Vasodilation and increased permeability.
Increased blood flow from vasodilation
- brings oxygen, nutrients, immune cells and repair substances
- Removes toxins and dead cells.
Increased permeability permits the movement of
- immune cells
- defence cells such as antibodies, and
- clotting factors into the tissue.
Stage 2: Emigration of phagocytes
Within an hour of the process beginning, phagocytes migrate to the scene (via chemotaxis).
* Neutrophils stick to the endothelium during vasodilation and squeeze through the vessel wall to reach the damaged area (leukocytosis).
* Monocytes quickly follow and transform into wandering macrophages.
* Dead phagocytes accumulate as pus
Stage 3: Tissue Repair
With regards to following inflammatory mediators, what are they released by and what is their function?
Histamine:
Leukotrienes:
Kinins:
Prostaglandins:
Histamine
Released by: Mast Cells and Basophils
Function:
- Increased permeability
- Vasodilation
Leukotrienes
Released by: Mast Cells and Basophils
Function:
- Increased permeability
- Attract Phagocytes
Mediator: Kinins
Released by? ???
Function:
- Increase permeability
- Induce vasodilation
- Attract phagocytes
- Induce pain
Mediator: Prostaglandins
Released by: Damaged Cells
Function:
- Locally-acting vasodilators
- prevent needless clot formation
- inflammation
- Ehance effects of histamine and kinins (and so intensify pain)
List TWO functions of non-specific fever.
a. Makes interferons more effective.
b. Inhibits growth of some microbes.
c. Speeds up the reactions that aid repair
Name the cytokine that induces fever.
Interleukin-1
Draw and label an ‘antibody
Y shaped structure that has 4 polypeptide chains, two binding sites, a contant region and a variable region.
