ABP Periodontal Pathogenesis and Host Response 2 — Questions and Answers
Question 1: Which cytokines are the principal mediators of osteoclast-driven bone resorption in periodontal disease?
- IL-4 and IL-10
- IL-1β and TNF-α (Correct answer)
- TGF-β and IL-13
- IL-6 and IFN-γ
Correct answer: IL-1β and TNF-α
IL-1β and TNF-α are the dominant pro-inflammatory cytokines that upregulate RANKL expression and directly stimulate osteoclastogenesis, driving alveolar bone loss in periodontitis.
Question 2: As the periodontal lesion progresses from gingivitis to chronic periodontitis, the predominant infiltrating immune cell transitions through which sequence?
- Macrophages → neutrophils → plasma cells
- Neutrophils → T lymphocytes → B cells and plasma cells (Correct answer)
- B cells → T cells → neutrophils
- Plasma cells → macrophages → neutrophils
Correct answer: Neutrophils → T lymphocytes → B cells and plasma cells
Per Page and Schroeder's staging, the initial/early lesions are dominated by neutrophils and T lymphocytes, while the established/advanced lesion is characterized by B cells and plasma cells as the primary infiltrate.
Question 3: RANKL contributes to alveolar bone destruction in periodontitis primarily by:
- Inhibiting osteoclast apoptosis through TRAP enzyme upregulation
- Stimulating osteoblast differentiation from periodontal ligament cells
- Activating osteoclast precursor differentiation and osteoclast resorptive activity (Correct answer)
- Sequestering osteoprotegerin to prevent it from binding to RANK
Correct answer: Activating osteoclast precursor differentiation and osteoclast resorptive activity
RANKL binds to RANK on osteoclast precursors, triggering their differentiation into mature osteoclasts and activating their bone-resorbing capacity, a process blocked by the decoy receptor osteoprotegerin (OPG).
Question 4: In active periodontal disease sites, the RANKL-to-OPG ratio is:
- Decreased, favoring net bone formation
- Unchanged compared to periodontally healthy tissue
- Increased, tipping the balance toward net bone resorption (Correct answer)
- Highly variable with no consistent directional change
Correct answer: Increased, tipping the balance toward net bone resorption
Periodontitis sites show elevated RANKL and suppressed OPG production from PDL fibroblasts and osteoblasts, resulting in a high RANKL:OPG ratio that favors osteoclastogenesis and bone loss.
Question 5: Matrix metalloproteinases (MMPs) contribute to periodontal tissue destruction primarily by:
- Stimulating fibroblast collagen synthesis and tissue repair
- Degrading extracellular matrix components including type I and III collagen (Correct answer)
- Directly activating the classical complement cascade
- Inhibiting osteoclast recruitment to alveolar bone
Correct answer: Degrading extracellular matrix components including type I and III collagen
MMPs, particularly MMP-1, -2, -8, and -13, cleave fibrillar collagens and other ECM proteins in the periodontal ligament and connective tissue, irreversibly destroying the structural attachment apparatus.
Question 6: Which complement activation pathway is primarily triggered by bacterial lipopolysaccharide (LPS) present in the periodontal pocket?
- Classical pathway initiated by C1q binding to antigen-antibody complexes
- Lectin pathway activated by mannose-binding lectin (MBL)
- Terminal pathway via direct activation of the membrane attack complex
- Alternative pathway via spontaneous C3 hydrolysis amplified by LPS (Correct answer)
Correct answer: Alternative pathway via spontaneous C3 hydrolysis amplified by LPS
LPS from gram-negative periodontal pathogens preferentially activates the alternative complement pathway through C3 tickover, and P. gingivalis gingipains further dysregulate complement to evade its effector functions.
Question 7: Prostaglandin E2 (PGE2) contributes to periodontal bone destruction primarily through:
- Inhibition of MMP secretion from gingival fibroblasts
- Direct stimulation of osteoblast bone matrix synthesis
- Enhancement of RANKL expression and osteoclast activation (Correct answer)
- Blocking pro-inflammatory cytokine production via negative feedback
Correct answer: Enhancement of RANKL expression and osteoclast activation
PGE2, produced in large quantities at inflamed periodontal sites, upregulates RANKL on stromal cells and osteoblasts while suppressing OPG, creating an environment that strongly favors osteoclastogenesis and bone loss.
ABP Periodontal Pathogenesis and Host Response 2
Which cytokines are the principal mediators of osteoclast-driven bone resorption in periodontal disease?