Biology - Immune system

Flashcards for the immunes system in Unit 4 outcome 1 for VCE biolody Units 3 &4

The five transmissiona nd entry points for pathogens

Peron to person contact,

airborne droplets

contact with contaminated food, object, or blood

ingestion of contaminated food or water

vectors that carry pathogeni agents and spread them to people

Pathway for disease to occur

Pathogen gains entry to the organism

Reaches target cells

Overcomes body defence system

Becomes established at one or more sites

Multiply rapidly

Cause harm to the host and produce symptoms of the disease

What does innate mean?

Existing since birth

What does non-specfic mean?

It is a general barrier that does not target specific pathogens

What 3 barriers does the first line of defence have?

Physical, chemical, microbiota

How is the first line of defence described?

Innate and non-specific

What are the 3 physical barriers in animals?

Epiphelial cells, Mucus membranes, sneezing and coughing

Epiphelial cells

Dead cells that line the skin, respiratory, gastrointestinala and urogenital tract to prevent entry of pathogens

Intact skin

Mucous membranes

Line tracts like nose, trachea, and lungs. They secrete mucous to trap invading pathogens whicha re swept out of the body by cilia.

Sneezing, coughing, vomiting

Expel foreign microbes from the body, known as a mechanical barrier

Microbe

Microscopically small orgnaisms

What are the 4 physical barriers in plants?

Thick bark, cellulose cell wall, stomata, formation of galls

Thick bark

Thick bark on trunks and fatty substances like waxes located on leaves prevent entry of pathogen

Cellulose cell wall

Protects plant from invading pathogen

Somata

Can be signalled to close to prevent entry of pathogen through opening

Formation of galls

Swelling on plant

What are the 3 chemical barriers in animals?

Stomach acid, sweat, tears and saliva excretion, fluid in lungs

Stomach acid

Contains hydrochloric acid strong enough to kill pathogens that have been consumed or entered the stomach after being caught by mucus.

Sweat, tears, slaiva

Contain lysozyme enzyme that breaks down bacterial cell walls

Fluid in lungs

Containsprotein surfactants that coat pathogens, making them easier for adapive immune system to eliminate them.

What are the 6 chemical barriers in plants?

Chitinases, phenols, defensins, tannins, caffeine, Citronella

Caffeine

In tea, coffee, and cocoa plants and is toxic to insects and fungi

Citronella

In lemongrass and repels insects

Microbiota barriers

Normal microbiota live on the surfaces of our body to prevent colinisation of other pathonogenic microogranisms by taking up space and consuming resources.

When does the second line of defence innitiate?

After microbes have gotten past the first line of defence and entered the body

Where does the second line of defence occur?

Mainly at the site of infection

What does the second line of defence react against?

Microbes, not toxins or other foreign material

What is inflammation?

The accumulation of fluid, plasma proteins and leukocytes that occurs when tissue is damaged or infected.

Symptoms of inflammation?

Pain

redness

heat

swelling

What are leukocytes?

White blood cells

What are the cells of the immune system calssified as?

Leukocytes

What is a phagocyte?

White blood cells that engluf foreign matter via endocytosis, and is the first to arrive at the site of infection.

Name the 3 phagocytes

Macrophages, neutrophills, dendritic cells

Phagocytosis

The process where a phagocyte engulfs a microbe and breaks them down into harmless products

What is a granulocyte?

leukocytes with granules that have enzymes that are released during infections, allergic reactions, and asthma.

Name 4 granulocytes

Neutrophills, eosinophils, mast cells, basophils.

What is an antigen presenting cell?

Phagocytes that digest foreign material containing an antigen and display a fragment of this antigen on the surface of their membrane where it can be recognised by the adaptive immune response.

What is an antigen?

Antigens are any substance that triggers and immune response in the body

What are cytokines?

Small signalling molecules released by body cells in response to damage or presence of a pathogen. They trigger innate responses associated with the second line of defence such as inducing inflammation and fever along with activating macrophages.

What is a macrophage?

Large phagocyte that engulfs mocrobes, digests them, and displays a fragment of it on their surface, becoming antigen presenting cells.

Where are macrophages located?

Located close to pathogen entry points

How do macrophages innitiate the immune respons?

Releases cytokines to innitiate the inflammatory response.

Where are neutrophills located?

In the bloodstream

What do neutrophills do?

They are relatively small in size and short lived and engulf microbes and kill them with toxic chemicals. They also release cytokines to attract other immune cells to the site of infectiona nd cause inflammation.

What are dendritic cells?

Small antigen presenting phagocytes that move through the body via the lymphatic vessels to lymph glands where they act as APC’s to the adaptive immunity cells, and secrete antiviral cytokines.

Where are dendritic cells located?

Located in tissues that have contact with the outside environment.

Eosinophil

Release cytotoxic chemicals from granules ontot he surfae of their targets,and release cytokines to attract more immune cells to the site of inflammation. Key in defence against alrger parasites.

Basophil

Granulocyte which releases histamine and other molecules as part of the inflammatory response.

Cytotocxic chemicals

Chemicals that break down the cytoplasm in invading cells

What do natural killer cells do?

Recognise and attack cells that do not contain a self marker because the MHC-1 marker ahs been altered or removed.

What do natural killer cells defend against?

Virus infected cells and cancer cells

How do natural killer cells attack cells?

NKC contain granules that are filled with cytotoxic chemicals such as perforin, which punches holes in cell membranes and triggers apoptosis.

Where are mast cells located?

In the connective tissues close to external environment and known as “border guards”

What is the role of mast cells?

To raise the alarm that a pathogen has entered the body by recognising pathgoens early and releasing cytokines that attract other immune cells tot he infection site.

How do mast cells work?

When a pathgoen is detected, a mast cell containing granules which contain histamine and other active molecules releases it during inflammation.

What are complement proteins?

Proteins that are dissolved in plasma of blood and circulate the body in an inactive form until they are activated by an antigen or a signal from an immune cell.

What happens when a complement protein is activated?

A cascade affect occurs, once activated proteins adhere to the invading microorganism making it more readily identifiable as foreign phagocytes will be attracted to the site of infection.

What is the affect of complement proteins also known as?

Opsonisation

What is the second affect of complement proteins?

They also degranulate mast cells, causingthem to release histamine, causing inflamamtion.

What are interferons?

A type of cytokine that is released by cells infected with ciruses to signel other neighboring cells to heighten their antiviral defences.

How do cells heighten their antiviral defences when compelled to by an interferon?

The cell will decrease its membrane permeability so that viruses cannot enter the cell as easily.

Lysis

The breakdown of a cell due to damage to the plasma membrane

What is the second thing that interferons do?

They attract natural killer cellls to the site to release cytotoxins to kill the infected cell and activate macrophages to clean up the cell debris after lysis of an infected cell.

Whata re the steps to the inflammatory response?

1- A pathogen such as bacteria breaches the first line of defence

2- Injured cels at site of breach release cytokines that attract neutrophils, platelets release clotting factors at the site of wound, mast cells release histamine which increases blood vessel dilation and permeability.

3- The dilated, more permeable blood vessels allow leukocytes and molecules including complement proteins to enter infected tissue

4- Neutrophils migrate towards cytokines and are activated, causing them to phagocytose the pathogen and debris, degranulate and secrete factors that kill pathogens and release cytokines to attract macrophages to the site

5- Macrophages become activated, secrete cytokines and phagocytose pathogens and debri at site of infection. This can lead to the production of pus,combination of leukocytes, dead pathogens and cell debri.

6-Inflammatory response continues until pathogeng is eliminated and the wound is healed.

Vasodilation

Widening of blood vessels

Simplified version of the inflammatory response

1-Pathogen breaches first line of defence

2- Injured cells at site of breach release cytokines which promote the migration of phagocytic cells sucha s neutrophils and macrophages to the area, platelets secrete clotting factors, and mast cells are activated to release histamine

3- Histamine increases blood vessel dilation and permeability, causing redness, swelling, heat, and increased blood flow to the area, as well as allowing leukocytes and complement proteins to enter the infected tissue

4- Phagocytic cells continue to engulf and destroy pathogens, and the inflammatory response continues until the pathogen is eliminated and the wound is healed

What is a pathogen?

An organism that can cause sickness or diease in another organism

What is an antigen?

A unique molecule or part of a molecule that is recognised by the immune system and can innitiate and immune response.

Where can antigens be found?

Most antigens can be presented on the surface of the plasma membrane, but some antigens such as toxins released by bacteria circulate freely in body fluids.

self-antigen (Self markers)

Antigens expressed by cells belonnging to an organism (Have originated from an organism

Non-self antigens

Antigens that have not originated from and organism and therefore do not belong to that organism.

What are MHC markers?

Major Histocompatability Complex markers are proteins on the surface of your body cells and are split into two main groups.

MHC-1 markers

Present on the surface of all nucleated cells of your body excluding red blood cells.

MHC-2 markers

Are found only on the surfaces of specific white blood cells known as the professional antigen presenting cells. Macrophages, dendritic cells, and B lymphocytes.

Process of phagocytosis

1- Phagocyte is activated by cytokines or by chemicals the microbes give off

2- Adherance of pathogen antigen to phagocyte induces membrane potrusions to extend around microbe

3- Microbe is fully enclosed in a membrane results in phagosome (phagocytotic vesicle) \

4- A pathogen moves into cell interiors, lysosomes bind with phagosome to form phagolysosome.

5- Enzymes, like lysozyme, break down and digest microbe.

6- Formation of residual body with undigested material

7- Leftover debri is discharged by exocytosis.

What are antigen presenting cells?

Cells that display fragments of undigested antigens from forign/non-self substances on their MHC-2 markers on the surface of their plasma membrane.

What line of defence does MHC-2 amrkers signal to?

The third line of defence, adaptive immune response.

Cellular pathogens

Pathogens that have a cellular structure and are capable or reproducing without the use of a host cell.

Examples of cellular pathogens

Bacteria, fungi, protozoa, parasites, anthropods

Non-cellular pathogens

Pathogens that do not have cellular structure and need a hsot cell to reproduce.

Examples of non-cellular pathogens

Viruses, prions, and viriods

What are bacteria

Prokaryotic organism that may have an external capsule for extra protection and replicate using binary fission.

Gram positive bacteria

Gram stain blue and can be killed by antibiotics

Gram negative bacteria

Gram stain pink and cannot be killed by antibiotics

What do bacteria produce?

Spores, and toxins that can damage particular tissues fo their host organism

Exotoxins

Highly toxic soluble proteins produced by the bacteria and release into the surroundings

Endotoxins

Released when the outer membrane breaks down

Protists/ Protozoan

Unicellular eukoaryotes that reproduce with binary fission. Cause dieseases such as malaria, usually transferred via vector.

Fungi

Eukaryotic organisms that reproduc asexually and secrete digestive enzymes and chemicals to break down food. Causes disease such as tinea and thrush

Parasites

Multicellular eukaryotes that reproduce asexually and depend on host for survival. Include roundworms, tape worms.

Viruses

Have no celllar structure, don’t metabolize their own energy, and depend on hsot cell for survival. They contain genetic material surrounded by protein covering.

Prions

Smallest known pathogens that do not contain genetic material. Is produced when a normal cellular protein is converted to an infectious harmful form due to incorrect folding. Mad cow disease.

Viroids

Pathogenic to plants and composed of short circular strands of DNA that interfere with the internal structure of plants.

What is an allergen

Any antigen that elicits an allergic response.

What is an allergic response

Specific type of immune response where the immune system overeacts to a normally harmless substance.

What is the third line of defence classified as?

Specific and aquired

Specific

Specific tot he pathogen that has breacehd botht eh first and second line of defence

Aquired

An immunity that develops when an immune response occurs

What is the lymphaic system?

A network of tissues and organs across the body tha work in conjunction with the circulatory and immune system to fight infection.

Main roles of the lymphatic system

Return fluid ot the blood

Filter tissue fluid

Be a site of antigen recognition

Transport leukocytes aroudn the body

Be a site of lymphcyte maturation