Topic 2: Infectious Disease

Question 1

identify the difference between infectious diseases and non-infectious diseases and provide examples of each

Answer 1

Disease: Any deviation from the normal structure or function of any body part,
organ or system that is manifested by a characteristic set of symptoms.
Infectious disease: caused by invasion of a pathogen and can then be transmitted
from one host to another.
Non-infectious diseases are caused by genetic and lifestyle factors.

EXAMPLES
Non-infectious: cancer, Alzheimer’s disease and epilepsy

Infectious: Chickenpox, Common cold, Covid-19

Question 2

define pathogens

Answer 2

Pathogen: A causative agent of disease (NOT organism)

Question 3

describe the following virulence factors that aid in pathogenesis: adherence
factors, invasion factors, capsules

Answer 3

Adherence factors: Adhesion is the ability to adhere to host cells. many pathogenic bacteria colonise mucosal sites by using pili to adhere to cells.

Invasion factors: The ability of a pathogen to enter a host’s tissues, multiply and
spread to other tissues.

capsules: Allow pathogens to resist host immune defence by preventing phagocytes from adhering to them. Many bacteria are surrounded by capsules that protect them from opsonisation and phagocytosis.

Question 4

Define disease

Answer 4

Disease is a physiological abnormality or significant disruption in thehealth of an individual. It is caused by a variety of factors, such asgenetic predisposition, environmental conditions, poor nutrition andby pathogens

Question 5

What types of changes do pathogens cause in host cells?

Answer 5

When a pathogen (including bacterial and viral) enters a host, it causes physical or chemical changes (for example, the introduction of foreign chemicals via the surface of the pathogen, or the production of toxins) in the cells or tissues; these changes stimulate the host immune responses

Question 6

What are some examples of physical defence strategies and chemical defence strategies of plants in response to the presence of pathogens? (give a brief explanation)

Answer 6

• Physical defences
  Waxy cuticle
  Bark woody stems
• Chemical defences:
  Production of toxins that are harmful to pathogens (e.g. named example:
  the insecticide pyrethrin).
  Production of defensins which have antimicrobial properties that inhibit
  pathogen growth.

Question 7

What does the innate immune response comprise of?

Answer 7

(Surface barriers)
These are barriers which aim to keep pathogens out of your body or limit
their ability to spread and move throughout the body.
Physical barriers: skin; mucus membranes, cilia, eyelashes. blood
Defence mechanisms: secretions, mucus, bile, gastric acid, tears, and sweat.

(Internal barriers)
Complement system
Neutralisation: Blocking adhesion of pathogens to cells.
Opsonisation: Marking pathogens so phagocytes can easily find them.
Cell lysis: Cause damage the plasma membranes of the pathogen.
Chemotaxis: Attract other immune cells to the infected area.

(Inflammation)
Mast cells secrete histamine and prostaglandins that cause vasodilation, allowing increased blood flow permeability to the area. Histamine also increases permeability of the capillaries, allowing Natural plasma, proteins and white blood cells (such as phagocytes and natural
killer (NK) cells) into the infected area.

Question 8

describe the inflammatory response (prostaglandins, vasodilation,
phagocytes)

Answer 8

a response of the body to an injurious agent, characterised by swelling, pain or heat. Prostaglandins are a chemical released from damaged cells that directs blood flow to an injured area. Vasodilation is the dilatation of blood vessels, which decreases blood pressure. Phagocytosis is usually followed by inflammatory pathway activation, which promotes pathogen elimination and inhibits pathogen growth.

Question 9

What are the differences and similarities between passive immunity and active immunity for both naturally and artificially acquired immunity?

Answer 9

Passive immunity is antibodies
gained via the placenta (natural) and via antibody serum injection (artificial)

active immunity is acquired via (natural) exposure to a pathogen or through the use of vaccines (artificial)

Question 10

What is the transmission of disease facilitated by? Give examples

Answer 10

the transmission of disease is facilitated by regional and global
movement of organisms.
Local, national and global movement of humans
Natural movement of animals via migration
Transport of pathogens can occur via water and wind.

Question 11

What are the interrelated factors affecting immunity?

Answer 11

• Persistence of pathogens within host
• Transmission mechanism
• Proportion of the population that is immune or has been immunised
• Herd immunity
• Mobility of individuals in the affected population.

Question 12

What is MHC (major histocompatibility complex)?

Answer 12

All the cells in an organism have special protein molecules called the MHC (major histocompatibility complex) on their outer membrane. It is a kind of self-marker or identity tag. The immune system can therefore recognise ‘self’ (all body cells of an individual have exactly the same MHC I on their surface). MHC II proteins are found only on certain cells, such as macrophages and B-lymphocytes, and are used in the recognition of foreign cells. Cells not containing the specific MHC I for the individual are not recognised and therefore attacked by the immune system

Question 13

Define disease

Answer 13

Disease is any deviation from the normal structure or function of any body part, organ or system that is manifested by a characteristic set of symptoms.

it is a physiological abnormality or significant disruption in the health of an individual. It is caused by a variety of factors, such as genetic predisposition, environmental conditions, poor nutrition and by pathogens

Question 14

What is the complement system?

Answer 14

A class of proteins in the blood plasma that identifies potential pathogens and activates the inflammatory response to an infection. During some bacterial infections, the proteins help kill bacteria by making holes in the bacterial membrane.

Question 15

What is the humoral response

Answer 15

Humoral response involves B lymphocytes and results in the production of antibodies that act against the pathogen. Memory cells are produced

Effector B cells secrete antibodies

Memory cell/lymphocyte: once activated by antigens, produce plasma cells that can secrete large amounts of antibody into the blood if there is another infection.

Question 16

What are B-lymphocytes

Answer 16

a white blood cell that does not pass through the thymus as it matures; involved in antibody formation

Question 17

What are the 5 stages of the inflammatory response?

Answer 17

pain, heat, redness, swelling, and loss of function

Question 18

What is the acquired immune system?

Answer 18

immunity that is not present at birth but is ‘learned’; the learning process starts when a person’s immune system encounters foreign invaders and recognises non-self substances (antigens) – the system then generates special chemicals (antibodies) that neutralise the pathogen. Includes the cell-mediated and humoral response systems. Memory cells are produced in both of those responses.

Question 19

What is the cell-mediated response?

Answer 19

The cell-mediated response involves mostly T-lymphocytes. Antigens stimulate the production of T-lymphocytes in the thymus gland. On contact with the complementary antigen of foreign matter, these sensitised cells release soluble proteins (lymphokines – a type of cytokine) into the body fluids.

Question 20

What are T-lymphocytes?

Answer 20

a lymphocyte that has passed through the thymus during maturation

Question 21

What is the humoral response?

Answer 21

Humoral response involves B lymphocytes and results in the production of
antibodies that act against the pathogen. Memory cells are produced.

Question 22

What is Gammaglobulin?

Answer 22

A type of antibody

Question 23

What is Gammaglobulin?

Answer 23

A type of antibody in the humoral response

Question 24

What is the humoral response?

Answer 24

Humoral response involves B-lymphocytes and results in the production of antibodies that act against a pathogen. Memory B cells are produced.

Question 25

what is natural active and natural passive immunity?

Answer 25

natural active immunity occurs when a person is exposed to a live pathogen and develops a primary immune response, which leads to immunological memory. Natural passive immunity is antibody-mediated immunity conveyed to a foetus or infant by its mother

Question 26

what is natural active, natural passive immunity, artificial active immunity and artificial passive immunity?

Answer 26

natural active immunity occurs when a person is exposed to a live pathogen and develops a primary immune response, which leads to immunological memory. Natural passive immunity is antibody-mediated immunity conveyed to a foetus or infant by its mother. Artificial active immunity is an active immunity acquired by vaccination with a vaccine containing active antigens to prevent the development of the disease in the future. Artificial passive immunity immunity is acquired by means of injection of serum containing antibodies into an individual who may have been infected with a particular pathogen.

Question 27

What is the cell-mediated response?

Answer 27

Cell-mediated response involves T lymphocytes which destroy infected cells. MemoryT cells are produced.

Memory T cell/lymphocyte: survive for many years and very quickly
us create cytotoxic T cells and helper T cells when the person is exposed to
the pathogen again, producing a faster and stronger immune response.

Question 28

What is an auto-immune disease?

Answer 28

a disease in which the body produces antibodies that attack its own tissues.

Question 29

Give a brief explanation of viruses.

Answer 29

Viruses
o Depend on other cells to reproduce.
o Made up of a DNA or RNA genome, coated with a protein shell called capsid.
o Some have an external lipid membrane envelope.

Question 30

give a brief explanation of bacteria in relation to pathogens

Answer 30

Prokaryotic organisms that have a cell wall but no nucleus or membrane bound organelles

Question 31

Give a brief explanation of fungi in terms of pathogens

Answer 31

Fungi

o Eukaryotic organisms that secrete enzymes on their host, externally digest their food and then absorb the nutrients.

Question 32

Give a brief explanation of protists.

Answer 32

Protists
o Eukaryotic organisms that normally do not cause disease, but approximately 24 are pathogenic parasites that have to infect other organisms to reproduce.

Question 33

Give a brief explanation of parasites.

Answer 33

Parasites
o Eukaryotic organisms that live on or in another organism, called the host, ° Capsules: Allow path
and obtain nourishment at the expense of the host.

Question 34

Give a brief explanation of Prions.

Answer 34

Prions
o The smallest of all pathogenic molecules. They’re the only known
infectious agents that do not contain any genetic material.
A prion is a type of protein that can trigger normal proteins in the brain to
fold abnormally. They are very similar to normal cellular prion proteins
(PrPs) that are found on CNS cell membranes but have a misfolded
structure.