The Immune System Revision

To revise for the Science exam

Human disease

A change that impairs an individual's function; it causes one harm

Non-infectious disease

Non-contagious, can't spread from person to person

Infectious disease

Contagious, can spread from person to person

Non-infectious disease types and example

Ageing - Heart disease
Cancer - stomach
Environmental - drug or accident related
Chemical (metabolic) - diabetes
Mental - Depression
Inherited - colour blindness
Nutritional - Obesity

Pathogen

An organism that causes disease

Cellular pathogen categories

Animals - lice
Fungi - tinea
Protozoa - Malaria
Bacteria - tuberculosis

Non-cellular pathogen categories

Viruses - chickenpox

Prions - mad cow disease

Vector

An organism that carries a pathogen between two other organisms, without being affected by the disease themselves.

Ways to prevent disease transmission

- Quarantine
- Hygiene
- Animal control
- Clean water
- Vaccination
- Waste disposal
- Food safety
- Treatment

Microbiome

all of the microorganisms that live in a particular environment, such as a human body. In the human body they are good bacteria that help us fight infection.

Gut flora

Bacteria that colonises our gut at birth

Different host types for parasites

Primary host - Adult stage

Intermediate (Secondary) host - Larvae stage

What are endoparasites?

Parasites that live within the body of their host.

What are ectoparasites?

Parasites that live on the external surface of a host.

What are prions?

Infectious proteins that convert normal protein to prion protein.

Are prions cellular or non-cellular?

Non-cellular

What happens to cells containing prions?

They burst and spread the prions further, and can also damage bodily tissues.

Diseases caused by prions

bovine spongiform encephalopathy (mad cow disease), Creutzfeldt-Jakob disease

Virus

- Non-cellular
- Contain genetic material (DNA or RNA)
- Protein coat (capsid)
- Disputed if living

Virus life cycle

1. Attatch to outside of cell
2. Shed protein coat and goes into cell, releasing nucleic acids
3. Host copies virus
4. New viruses are released

Bacteria cell shapes

-coccus (spherical)
-spirochaete (spiral-shaped)
-bacillus (rod-shaped)

What are protozoans?

• Unicellular organisms

• Can be free-living or parasitic

• Often found in moist environments

• Much larger and more complex than bacteria

What diseases are caused by protozoans?

Head lice, malaria, and amoebic dysentery.

Fungi

- Cellular
- Many are parasites
- E.g. Tinea, athlete's foot

Antigens

Molecules on the surface of all cells, each one being unique, that allows the body to identify the cells as either self or non-self

1st line of defence

Non-specifically keeps pathogens out

Physical barriers

skin, cilia, nasal hairs

Chemical barriers

saliva, tears, acid and mucus

Another name for tear ducts

Lachrymal glands

2nd line of defence

Non-specifically recognises and eliminates pathogens. Inflammation, fever, phagocytosis: explain

Inflammation

Due to increased blood flow, when cells in the skin's dermis release histamine to bring blood and white blood cells to the site of infection

Phagocyte

A special type of white blood cell, capable of engulfing and destroying pathogens using lysosomes, in a process called phagocytosis

Lysosomes

Organelles in phagocytes that contain a digestive enzyme, lysozyme, that can break down foreign materials

3rd line of defence

Detects specific pathogens and destroys them using memory cells and lymphatic system - produces lymphocytes which can remember, identify, immobilise and kill specific pathogens

Lymphatic system

lymph vessels, lymph nodes, lymph and white blood cells. Most of these white blood cells are lymphocytes

B lymphocytes (humoral immunity)

form in the bone marrow and divide into plasma cells to produce specific antibody proteins to immobilise pathogens

Antibodies

Produced by B lymphocytes, bind to their matching antigen, causing pathogens to clump together to help phagocytes to engulf them

T lymphocytes (cell-mediated immunity)

Fight on cellular level, either cytotoxic, helper or regulatory

Cytotoxic t-cells

Excretes cytokines to directly kill infected cells, pathogens, cancerous cells

Helper t-cells

Secretes substances to stimulate B cell antibody production, T cell activation and T cell growth

Regulatory t-cells

moderate immune response

What are memory cells?

B lymphocytes that remain dormant until reactivated by the same antigen.

What is the function of memory cells?

They remember specific antigens to respond faster to re-infection.

How quickly can memory cells respond to re-infection?

Sometimes fast enough to not even see any disease symptoms.

Immunity

the resistance to a particular disease-causing pathogen

Active immunity

Immunity gained when your body makes antibodies to a specific antigen
- either natural or artificial
- Memory cells produced

Natural active immunity

Antibodies made after exposure to antigen

Artificial active immunity

Antibodies made due to vaccination

Passive immunity

Receiving antibodies from an outside source
- either natural or artificial
- NO memory cells produced

Natural passive immunity

Antibodies acquired by a child through placenta and breast milk

Artificial passive immunity

injection of antibodies

Vaccination

An injection that produces a mild form of a disease in order to make memory cells for the disease's antigens and increase speed of antibody creation if infection occurs

Herd immunity

When a large proportion of a population is vaccinated to a disease, it decreases the likelihood that the disease will spread between unvaccinated people

Pandemic vs. epidemic

Pandemic - outbreak of global proportions

Epidemic - a widespread occurrence of an infectious disease in a community at a particular time.