Immunology

Question 1

What are the key features of the Immune System?

Answer 1

• Able to specifically identify non-self and danger signals.
• Able to modify the response to deal with different pathogens.
• Able to actively promote tissue repair and healing.
• Able to remember any pathogen it encounters. (Immunological Memory)

Question 2

Name some constitutive barriers to infection?

Answer 2

• Skin.
• Mucous.
• Commensal Bacteria.

Question 3

Describe the skin barrier.

Answer 3

• Physical barrier: multi-layered, renewal and replacement.
• Physiological factors: low pH 5.5, low O2 tension.
• Sebaceous glands: secrete hydrophobic oils, lysozyme, ammonia, antimicrobial peptides.

Question 4

Describe the mucous barrier.

Answer 4

• Mucous membranes: Secrete mucous where cavities come into contact with the environment.
• Physical barrier: traps invading barriers.
• Secretory IgA: prevents Bac and Virus attaching and penetrating epithelial cells.
• Contains enzymes: lysozymes, defensins and antimicrobial peptides directly kill. Lactoferrin starve bacteria of iron.
• Cillia trap and physically remove pathogens.

Question 5

Describe the commensal bacteria.

Answer 5

• 100 trillion (10^14) normally reside at epithelial surfaces.
• Produce Bactercidins influencing other bacteria.
• Reduction in pH of large bowel.
• Competition for essential nutrients,
• Production of anti-microbial short-chain fatty acids.
• Synthesis of vitamins K and B12.

Question 6

How important are commensal bacteria?

Answer 6

• Eradication of normal flora with broad-spectrum antibiotics commonly result in infection.
• Organisms rapidly colonize an undefended ecological niche.

Question 7

How are constitutive barriers breached during health care?

Answer 7

• Insertion of intravenous lines, catheters, nasogastric tubes.
• Antibiotics.
• Anti-acids, nasal decongestants, anti-bacterial wipes.

Question 8

Name the Major Components of the immune system.

Answer 8

• Cells: Leukocytes, White blood cells.

- Soluble factors: Humoral factors.

Question 9

Name Phagocytes.

Answer 9

• Neutrophils.
• Monocytes and macrophages.
• Dendritic cells.

Question 10

Name Lymphocytes.

Answer 10

• T cells.
• B cells.
• Natural killer cells.

Question 11

Name other cells.

Answer 11

Mast cells, Eosinophils and Basophils.

Question 12

Name Humoral factors.

Answer 12

• Antibodies.
• Complement system proteins.
• Cytokines.
• Acute phase proteins.

Question 13

Cytokines.

Answer 13

• Diverse collection of small proteins and peptides produced in response to infection, inflammation and damage.
• Modulate behaviour of cells so play a key role in coordinating the immune system.
• Multiples overlapping functions.
• Short half-life.
• Local or systemic.

Question 14

Antibodies.

Answer 14

• Protein produced in response to specific antigen.
• Produced by antigen-activated B Cells.
• Defend against pathogens, viruses and toxins.

Question 15

T cells and B cells.

Answer 15

• Mature cells circulate through the blood, lymph, and secondary lymphoid tissues.
• Inactive until meet pathogen/antigen.
• Some are very long lived. (memory T and B).

Question 16

B Lymphocytes.

Answer 16

• Responsible for production and secretion of antibodies to defend against pathogens.

Question 17

T Lymphocytes.

Answer 17

• Helper T cells: Key regulators of immune system.

- Cytotoxic T cells: Kill virally infected body cells.

Question 18

Natural Killer cells.

Answer 18

• Large granular lymphocytes.
• Can detect and kill tumour cells and virally infected cells.
• Can kill antibody-bound cells/pathogens.

Question 19

Mast cells.

Answer 19

• Reside in tissues and protect mucosal surfaces.

Question 20

Basophils, Eosinophils.

Answer 20

• Circulate in blood.

- Recruited to sites of infection by inflammatory signals.

Question 21

Mast, Basophils and Eosinophils.

Answer 21

• Highly granular.
• Release Histamine, Heparin, and pro-inflammatory cytokines.
• Defense against pathogens that cannot be phagocytosed. (worms)
• Key role in mediating allergic responses.

Question 22

Complement system.

Answer 22

• Approx. 30 proteins.
• Produced in Liver.
• Circulate in blood as inactive precursors.
• Enter infected/inflamed tissues.
• Enzymatically cleave and activate more in biological cascade.

Question 23

Monocytes, Macrophages, and Neutrophils.

Answer 23

• Phagocytes.
• Ingest and clear debris from body.
• Important source of Cytokines.

Question 24

Monocytes.

Answer 24

• Circulate in the blood.

- Migrate to peripheral tissues and differentiate into macrophages.

Question 25

Macrophages.

Answer 25

• Long-lived tissue resident in phagocytes.
• Kupffer = Liver.
• Alveolar = Lung.
• Mesangial = Kidney.
• Microglial = Nervous.
• Limit inflammation, tissue repair, antigen presentation.

Question 26

Neutrophils.

Answer 26

• Phagocytic cells that circulate in the blood.

Rapidly recruited into inflamed, damaged, and infected tissues.

Question 27

Dendritic cells.

Answer 27

• Present in peripheral tissues in an immature state.
• Phagocytose antigens.
• Mature and migrate into secondary lymphoid tissues where they play a key role in antigen presentation.

Question 28

Comparing dendritic, macrophage, and neutrophils.

Answer 28

• Neutrophils: Complete destruction of proteins are seen.
• Dendritic: Partially degraded for antigen presentation and stimulation of adaptive response.
• Macrophages: Neutral = Clearance of dead host cells.
  Activated = phagocytosis of pathogens.
  Repair = reduced activity, produce pro-inflammatory cytokines.

Question 29

Primary Lymphoid Tissues.

Answer 29

• Sites of Leukocyte development.

Question 30

Where do Lymphocytes mature and circulate?

Answer 30

• Mature: bone marrow or thymus.

- Circulate: between blood, secondary peripheral lymphoid tissues and lymph.

Question 31

What are the immunological precursors found in bone marrow?

Answer 31

• Hematopoietic stem cells.

Question 32

Secondary Lymphoid Tissues.

Answer 32

• Sites where T cells and B cells become activated by antigen. (initiates adaptive immunity).

Question 33

Name secondary lymphoid tissues.

Answer 33

• Lymph Nodes: imp stations for monitoring tissues infections.
• Spleen: imp in monitoring blood-borne infections.
• Mucosal: associated lymphoid tissues.

Question 34

Lymphatic system.

Answer 34

• System of vessels draining lymph fluid from body tissues.

Question 35

Lymph.

Answer 35

• Derived from blood plasma in tissues.

- Drains back to blood via lymphatic vessels and the right subclavian vein.

Question 36

Lymph Nodes.

Answer 36

• Positioned along lymph vessels to monitor the lymph for signs of infection.

Question 37

Lymphoedema.

Answer 37

• Lymphatic obstruction.
• Inherited, cancer treatment and parasitic infections.
• At increased risk of infection.

Question 38

Immune system compromised of two arms.

Answer 38

• Innate Immune.

- Adaptive Immune.

Question 39

Innate Immune system.

Answer 39

• Acute inflammation.
• Macrophages.
• Mast cells.
• NK cells.
• Neutrophils.
• Complement.
• Leads to Dendritic cells.

Question 40

Adaptive Immune system.

Answer 40

• B cells, Antibodies.
• T cells.
• D cells and macrophages present antigens.
• Activates T cells.
• T cells produce cytokines that help phagocytes.
• B cells produce antibodies that coat bacteria and help phagocytes.

Question 41

Innate system response.

Answer 41

• Rapid response (mins-hrs).

- Generic biological response is produced in response to many pathogens.

Question 42

Adaptive system response.

Answer 42

• Slow response (days).
• A unique response for every pathogen.
• Mediated by T and B cells.
• Responsible for immunological memory.