Immunology

Question 1

What are THREE roles commensal bacteria play in periodontal defence?

Answer 1

• Competitive barrier (nutrients, ecological niche)
• Physical barrier
• Immunological barrier (constant sampling “state of perpetual excitement” and tolerance to commensals)

Question 2

What’s so bad about High Endothelial-like Venules (HEVs)?

Answer 2

They are lumpy vessels that produce turbulent flow to allow WBCs to transmigrate through endothelium into site. The angiogenesis of HEVs may explain greater inflammation at sites of periodontitis.

Question 3

What are THREE bacterial virulence factors that may trigger an immune response in gingivitis/periodontitis?

Answer 3

• LPS
• Lipotechoic acid
• Proteases (e.g. MMP, gingipains)

Question 4

What do adhesion molecules have to do with perio pathogenesis?

Answer 4

They allow for greater transmigration of WBCs -> increased inflammation

Question 5

What are FOUR cells of the periodontium and their roles in perio pathogenesis?

Answer 5

• Gingival epithelial cells (sampling, tolerance, cytokine prodn, physical barrier)
• Fibroblasts (cytokine prodn)
• Monocytes (IL-6/8 prodn, precursor for macrophage, osteoclast, dendritic cells)
• Neutrophils (degranulation -> collateral damage)

Question 6

What are TWO mechanisms through which tolerance to commensal bacteria may be achieved?

Answer 6

• PAMP (pathogen associated molecular pattern) on commensal undergoes biochemical modification to render them ‘stealth’
• Commensals produce tolerance signals

Question 7

What are TWO things that detect MAMPs/PAMPs?

Answer 7

TLR (toll-like receptor) and PRR (pattern recognition receptor)

Question 8

What is the difference in PMNs in aggressive perio vs. chronic perio?

Answer 8

• High PMN count in aggressive perio

- Low or faulty PMN in chronic perio

Question 9

What are TWO cytokines involved in osteoclast differentiation and activation?

Answer 9

• M-CSF (Macrophage colony stimulating factor)

- RANKL (from osteoblasts and T-cells)

Question 10

Describe the THREE components in the immune response process in periodontitis.

Answer 10

1. Activation and cytokine release from gingival cells, mast cells, endothelial cells, fibroblasts, monocytes
2. Vascular changes (PMN migration) and RANKL (osteoclast activation)
3. Adaptive immune system activated

Question 11

What is ONE mechanism to explain the link between periodontitis and Rheumatoid Arthritis?

Answer 11

1. P.gingivalis citrullination of host or bacterial proteins
2. Anti-citrullinated protein antibodies formed
3. Auto-immune attack of citrullinated host proteins in joints

Question 12

What are FOUR steps through which cigarette smoke promotes chronic inflammation at the periodontium?

Answer 12

1. Cigarette smoke triggers epithelial cells to release pro-inflammatory cytokines
2. Cytokines recruit and promote survival of innate immune system cells (neutrophils, macrophages) that release more pro-inflammatory cytokines
3. Result is chronic inflammation, impaired innate and altered adaptive
4. Adaptive immune system more likely to be autoreactive

Question 13

What are FIVE requirements for successful eradication of a virus?

Answer 13

• Available effective attenuated vaccine
• Antigen stable virus
• No assymptomatic carriers
• Absence of animal reservoir
• Public cooperation

Question 14

What are the general herd immunity thresholds?

Answer 14

80-95%, depending on specific disease.

Question 15

Vaccine-preventable diseases (measles and pertussis) are becoming more common. What are THREE reasons why?

Answer 15

• Anti-vax movement
• Waning efficacy of vaccines and pathogen adaptation
• Travel to endemic areas