Innate Immunity

Question 1

What is the difference between the two branches of immune system?

Answer 1

Innate:
- nonspecific
- rapid (few hours)
- no memory component
- born with

Adaptive:
- highly specific
- delayed (several days)
- memory component
- built

Question 2

What does the innate immune system consist of?

Answer 2

1. Physical barriers
2. Chemical defences
3. Cellular defences
4. Molecular defences
5. Physiological processes

Question 3

What is the innate immune system?

Answer 3

Branch of immune system that exists at birth, always present, and acts as natural host resistance

Question 4

Why do pathogens prefer a specific body site to initiate infection?

Answer 4

1. whether the site meets its nutritional and metabolic needs
2. based on the mechanism of spread

Question 5

What are the physical barriers to infection in the human immune system?

Answer 5

1. Skin
2. Mucous membrane of respiratory tract, digestive tract, reproductive tract, urinary tract

Question 6

How does skin act as a barrier to infection?

Answer 6

• rich in tough protective protein (keratin)
• slightly acidic (pH = 5)
• High [NaCl] with periodic drying

Question 7

What are mucous membranes and how do they act as a physical barrier to infection?

Answer 7

Line the tracts in your body and produce mucous via goblet cells that trap microbes and contain antimicrobial secretions

Question 8

How does the respiratory tract act as a physical barrier to infection?

Answer 8

Contains the mucocilliary escalator, made up of mucosal epithelial cells that contain cilia. They filter the incoming air, trap microbes in mucous, and sweeping action of cilia allow removal of mucous and trapped microbes from the lungs.

Question 9

How does the stomach act as a physical barrier to infection?

Answer 9

Strongly acidic (pH = 2) and contains proteases which create an environment difficult for microbes to survive in.

Question 10

How does the large intestine act as a physical barrier to infection?

Answer 10

Contains the normal resident bacteria that live symbiotically inside of the colon and use attachment sites to persist. Consume undigested nutrients (competitive exclusion) and produce antimicrobial compounds (microbial antagonism)

Question 11

How does the small intestine act as a physical barrier to infection?

Answer 11

Pancreatic juice buffers acidity of incoming contents from the stomach (pH = 7) and contain pancreatic enzymes. Small intestine also has bile from the liver which create an environment difficult for microbes to survive in.

Question 12

Difference between competitive exclusion and microbial antagonism

Answer 12

Competitive exclusion: Microbiota takes up niche (space and nutrients)

Microbial antagonism: actively eliminate competition

Question 13

How does the genitourinary tract act as a physical barrier to infection?

Answer 13

Urinary tract contains urine and includes many toxins that are intolerable by bacteria, and urination physically washes out bacteria.

Question 14

How does the female reproductive tract act as a barrier to infection?

Answer 14

Vagina contains normal microbiota that rely on glycogen secreted by epithelial cells and supplies nutrients,

Question 15

What is the lymphatic system?

Answer 15

Organs and vessels that allow immune cells to contact foreign antigenic material

Question 16

What is an antigen?

Answer 16

Foreign material that is able to activate cells of the immune system

Question 17

What are lymphatic vessels?

Answer 17

Vessels of lymphatic system that carry lymph from the tissues to the lymph nodes (unidirectional)

Question 18

What is lymph?

Answer 18

Liquid within lymphatic cells that are rich in leukocytes and free of erythrocytes.

Question 19

What is the difference between primary and secondary lymphoid organs?

Answer 19

Primary: produce (bone marrow) or mature (thymus gland) leukocytes

Secondary: filter and contain high concentration of leukocytes (e.g. lymph nodes, spleen, mucosa associated lymphatic tissue)

Question 20

What is Mucosa associated lymphatic tissue (MALT)?

Answer 20

Associated with all mucous membranes and may be specialized based on type of mucous membrane (e.g. Gut associated lymphatic tissue)

Question 21

What are leukocytes?

Answer 21

White blood cells that circulate in the blood and the lymphatic system that reside in the tissues and lymph nodes, and has a role in both innate and adaptive immunity.

Question 22

What are the categories of leukocytes?

Answer 22

Granulocytes: large visible reactive granules in cytoplasm that can kill microbes and serve as signalling molecules to recruit and activate other components of the immune system

Agranulocytes: contain cytoplasmic granules that are much smaller and more difficult to view than granulocytes

Question 23

What are the three types of granulocytes?

Answer 23

1. neutrophils
2. eosinophils
3. basophils and mast cells

Question 24

What is a neutrophil?

Answer 24

Strongly phagocytic granulocyte whose cytoplasmic granules contain lysozymes and defensins.

Question 25

What is an eosinophil?

Answer 25

Non-phagocytic granulocyte whose cytoplasmic granules stain with acidic dyes. They work to destroy large parasitic cells (protozoa/parasitic worms) by secreting extra-cellular enzymes and reactive oxygen species.

Question 26

What are basophils + mast cells?

Answer 26

Not strongly phagocytic granulocyte whose cytoplasmic granules stain with basic dyes. Basophiles circulate in the blood while mast cells reside in mucosal tissue. Both degranulate in response to stimuli and release histamine.

Question 27

What does histamine do?

Answer 27

Locally: causes vasodilation

Systemically: causes life threatening vasodilation and bronchiolconstriction.

Question 28

What are the types of agranulocytes?

Answer 28

Monocytes (macrophages and dendritic cell) and Lymphocytes (B cells, T cells, NK cells)

Question 29

What are macrophages?

Answer 29

Phagocytic monocytes that are located in the lungs, connective tissue, spleen and liver, and contain Toll-like-Receptors to recognize many pathogens with one receptor and induce phagocytosis

Question 30

What are Toll-like-Receptors (TLR’s)?

Answer 30

AKA pattern recognition receptors; surface proteins on phagocytic leukocytes that act as receptors that recognize pathogen associated molecular patterns (PAMPS) to trigger phagocytosis.

Question 31

What do pathogen associated molecular patterns (PAMP’s) include?

Answer 31

Lipopolysacharides (gram -ve), lipoteichoic acid (gram +ve), peptidoglycan, elements of fungal cell walls, and flagellin

Question 32

What are dendritic cells?

Answer 32

Phagocytic monocytes that are found in tissues that are often the sites of entry for infectious materials (langerhan’s cells in skin) as well as mucus membranes of nose, lungs and intestines. They regularly sample the surroundings and phagocytose antigens, carrying them to lymphoid organs and present it to T/B lymphocytes to activate the adaptive immune response.

Question 33

What is the difference between monocytes and lymphocytes?

Answer 33

monocytes are in charge of phagocytosing pathogens, whilst lymphocytes are in charge of inducing a specific immune response

Question 34

What are B lymphocytes?

Answer 34

Aka B cells or plasma cells; antibody secreting/producing cells that form the main component of humoral immunity (antibody mediated immunity)

Question 35

What are T lymphocytes?

Answer 35

aka T cells; many different types that form the main component of cell mediated immunity

Question 36

What are Natural Killer cells?

Answer 36

Destroy abnormal cells in the body (cancer cells, infected cells)

Question 37

What are the molecular defenses of the innate immune system?

Answer 37

Secretions at mucosal sites

Lysozyme: cuts beta-1,4 glycosidic bonds in peptidoglycan

Defensins: antimicrobial peptides that poke holes in bacterial cell membranes

Question 38

What is the process of phagocytosis?

Answer 38

1. Bacterium binds to the surface of phagocytic cell
2. Bacterium is engulfed into a phagosome via invagination of the cell membrane
3. phagosome fuses with lysosome which deposits lysozymes, defensins, proteases, lipases and nucleases to form phagolysosome.
4. Enzymes cleave macromolecules (oxygen independent killing) and generate reactive oxygen species (oxygen dependent killing)
5. Neutrophils perform exocytosis of debris and Macrophages/Dendritic cells present fragments of the intruder on the cell surface to become antigen presenting cells and trigger an adaptive immune response

Question 39

what are the five cardinal signs of inflammation and what is it a response towards?

Answer 39

Redness (erythema), warmth, pain, swelling (edema) and loss of function occurring due to release of pro-inflammatory cytokines by injured tissue and leukocytes in response to tissue damage, toxins, and infectious material

Question 40

What occurs during inflammation?

Answer 40

1. Blood vessels dilate to allow for leukocyte access
2. Vessel walls become more permeable for extravasation (leukocytes squeezing into tissues) and attacking invading pathogens
3. Temperature increases to slow the growth of pathogens and promotes faster healing of damaged tissues
4. Blood leaking into tissue spaces can clot to prevent movement of pathogens

Question 41

What is a fever? What does it result in?

Answer 41

Increase in body temperature (38°C-43°C) controlled by hypothalamus, triggered by toxins, LPS, and chemicals produced by the immune system. It results in muscle contraction, increased temp (faster metabolism and promoted healing) faster phagocytosis, and slower growth of microbes.