Immunity

Question 1

What are the nonspecific defences?

Answer 1

Physical Barriers
Phagocytic Cells
Immunological Surveilance
Interferons
Inflammation
Pyrexia

Question 2

What are specific defences?

Answer 2

Immunity

Question 3

What do pathogens include?

Answer 3

Viruses, Bacteria, Fungi, and Parasites which can potentially cause harm if allowed to multiply and/or spread

Question 4

What are antigens?

Answer 4

Pathogens, parts or products of pathogens, or other foreign compounds

Question 5

What are the physical barriers?

Answer 5

Prevent stuff entering
Skin
Hair
Secretions from Sebaceous/Sweat Glands
Mucus
Stomach Acid
Urine
Other glandular secretions that have enzymes, Ig, acidic pH

Question 6

What are phagocytes?

Answer 6

Cells in peripheral tissues that remove debris and respond to invasion
They can move between blood and interstitial fluids [in tissues]
First line of Cellular Defence

Question 7

What are the two types of phagocytes?

Answer 7

1) Macrophages engulf and destroy pathogens or debris [via lysosomes], bind and call for assistance, and release toxins
2) Microphages - include neutrophils [remove cellular debris and bacteria] and Eosinophils [remove pathogens covered with Ig]

Question 8

What is Immunological Surveillance?

Answer 8

Constant monitoring of normal tissues
Usually performed by Natural Killer [NK] Cells
NK Cells monitor and recognise foreign antigens on other cells or damaged, mutated cells [destroy plasma membranes containing abnormal antigens]

Question 9

What happens when antigens are found on a cell?

Answer 9

The cell is immediately destroyed
Any type of cell or tissue can be destoryed by NKs
NKs can also destroy cancer cell d/t Tumour Specific Antigen

Question 10

What is the term used to describe when NK cells are ineffective?

Answer 10

Immunological Escape

Question 11

What are Interferons?

Answer 11

Interferons are proteins released when viruses are present
Normal cells [when exposed] produce additional proteins that interfere with viral replication
This slows spread of virus, also increases activity of Macrophages

Question 12

What are the 4 signs of Inflammation?

Answer 12

1) Swelling
2) Redness
3) Heat
4) Pain

Question 13

What is Inflammation?

Answer 13

Mechanical or Chemical stress triggers release of Mast Cells within affected tissue
Mast Cells release Histamine and Heparin which initates Inflammatory Response
Result of Inflammation is replacement or repair of Damaged Tissue

Question 14

What is Pyrexia [Fever]?

Answer 14

Pyrexia is when body temperature is maintained above 37.8°C

Question 15

What causes Pyrexia?

Answer 15

1) Proteins in blood called pyrogens can cause rise in body temperature
2) Pathogens can act as pyrogens or cause their release by macrophages

Question 16

What is the danger of Pyrexia?

Answer 16

Sustained pyrexia above 41°C can damage many organ systems and tissues

Question 17

How can Pyrexia sometimes be beneficial?

Answer 17

Can accelerate immune functions
Increases blood flow
Makes environment hostile towards pathogens
Causes liver and spleen to sequester Iron and Zinc

Question 18

What is Innate Immunity?

Answer 18

Determined by Genetics and usually species specific
Present at Birth
“Throw everything and the kitchen sink at it”

Question 19

What is Acquired Immunity?

Answer 19

Not present at birth and can be Active or Passive

Question 20

What is Active Acquired Immunity?

Answer 20

Occurs after exposure to an antigen and is the result of the immune response
Natural [Exposure]
Artifical [Vaccine]

Question 21

What is Passive Acquired Immunity?

Answer 21

Product of transfer of antibodies from another
Natural [Mother’s Breast Milk]
Induced [Rabies]

Question 22

What are the four main properties of Immunity?

Answer 22

1) Specificity [recognises specific antigens]
2) Versatility [millions of different lymphocytes produced]
3) Memory [Memory cells remain after exposure so next response is swift and quick]
4) Tolerance [recognises self and non-self for target response; can develop over time in response to chronic exposure but will not “remember”]

Question 23

What is Cell-Mediated Immunity?

Answer 23

1) T-cells activated by exposure to antigen
2) T-cells recognise antigens via Major Histocompatibility Complex [MHC]
3) If cell is healthy, it is ignored; if unhealthy, T-cells are activated

Question 24

What are the different types of Major Histocompatibility Complexes [MHCs]?

Answer 24

Class I - “I’m Abnormal, Kill Me” [all nucleated cellls]
Class II - “I’m infected with dangerous antigen” [antigen presentinc cells, APCs]
Class III

Question 25

What are the different types of T-Cells?

Answer 25

1) Cytotoxic “Killer” T-Cells - Actively track down and kills invaders
2) Helper T-Cells - Coordinate specific and non-specific defences; stimulate antibody-mediated immunity
3) Memory T-Cells - remain in blood stream after threat has gone causing rapid response next time
4) Suppressor T-Cells - turn off or moderate the immune response

Question 26

What is Antibody-Mediated Immunity?

Answer 26

1) B-Cells result in production of antibodies to attack antigens
2) Once B-cells activated, they differentiate into plasma cells which actually produce the antibody
3) Like T-Cells, some Memory B-Cells remain after infection for a faster second response

Question 27

What is B-Cell Sensitisation?

Answer 27

1) Usually occurs in lymph tissue nearest site of injury/infection
2) Antigens are brought into the cell via endocytosis and subsequently appear on surface of B-cell bound to Class II MHC
3) B-Cell remains on “standby”n until it gets “OK” from Helper T-Cell

Question 28

What happens in B-Cell Activation?

Answer 28

1) Activated Helper T-Cell binds to MHC complex and begins secreting cytokines that promote B-Cell division. accelerate plasma cell formation and enhance Ig production
2) Plasma cells begin synthesising and secreting large quantities of antibodies [~100 million]

Question 29

What are the functions of antibodies?

Answer 29

1) Neutralisation - bind to pathogen so it doesn’t work
2) Agglutination & Precipitation - tie antigens together to make them insoluble
3) Attraction of Phagocytes - attracts phagocytes to destroy infected cells and tissues
4) Enhancement of Phagocytosis - Ig coating makes engulfing easier
5) Stimulation of Inflammation - stimulate Mast Cells and Basophils slowing the rate of Infection