Skin sensitization and dermal toxicity assessment MCQs With Answer

Introduction

Skin sensitization and dermal toxicity assessment MCQs With Answer is a focused practice resource tailored for M.Pharm students studying Pharmacological & Toxicological Screening Methods-II. This collection emphasizes mechanistic understanding, regulatory test guidelines and practical screening methods used to evaluate skin irritation, corrosion, sensitization and percutaneous absorption. Questions cover in vivo, in vitro and in chemico approaches (e.g., LLNA, DPRA, KeratinoSens, h-CLAT), OECD test guidelines, biomarkers, study design and interpretation of results like EC3 and stimulation index. Use these MCQs to consolidate core concepts, prepare for exams and build confidence in selecting appropriate assays and interpreting dermal toxicology data in research and regulatory contexts.

Q1. What is the primary difference between skin irritation and skin sensitization?

• Both are immune-mediated responses with immediate onset
• Irritation is a reversible, non‑immune inflammatory response; sensitization is an immune‑mediated allergic response with induction and elicitation phases
• Sensitization always causes necrosis, whereas irritation never damages tissue
• Irritation requires prior exposure; sensitization occurs on first contact

Correct Answer: Irritation is a reversible, non‑immune inflammatory response; sensitization is an immune‑mediated allergic response with induction and elicitation phases

Q2. Which assay is described by OECD Test Guideline 429 for assessing skin sensitization?

• DPRA (Direct Peptide Reactivity Assay)
• Human Repeat Insult Patch Test (HRIPT)
• Local Lymph Node Assay (LLNA)
• KeratinoSens assay

Correct Answer: Local Lymph Node Assay (LLNA)

Q3. In the LLNA, the EC3 value refers to:

• The effective concentration producing a threefold increase in lymphocyte proliferation compared to control
• The exposure concentration that causes 3% necrosis in skin tissue
• The cumulative dose over three exposures that elicits irritation
• The enzyme concentration required for three days of activation

Correct Answer: The effective concentration producing a threefold increase in lymphocyte proliferation compared to control

Q4. Which in vitro assay specifically measures activation of the Nrf2-mediated antioxidant response pathway in keratinocytes?

• DPRA (Direct Peptide Reactivity Assay)
• h-CLAT (human Cell Line Activation Test)
• KeratinoSens assay
• 3T3 NRU phototoxicity test

Correct Answer: KeratinoSens assay

Q5. The Magnusson and Kligman test is better known as which type of sensitization test?

• Local Lymph Node Assay
• Human Repeat Insult Patch Test
• Guinea Pig Maximization Test (GPMT)
• 3T3 Neutral Red Uptake test

Correct Answer: Guinea Pig Maximization Test (GPMT)

Q6. What is the main objective of a Human Repeat Insult Patch Test (HRIPT)?

• Determine dermal LD50 in humans
• Evaluate cumulative irritation only
• Detect potential for human skin sensitization and establish induction/elicitation in volunteers
• Measure transdermal absorption kinetics quantitatively in humans

Correct Answer: Detect potential for human skin sensitization and establish induction/elicitation in volunteers

Q7. Which apparatus is most commonly used to measure percutaneous absorption in vitro across skin samples?

• Franz diffusion cell
• Patch clamp chamber
• ELISA plate reader
• Flow cytometer

Correct Answer: Franz diffusion cell

Q8. The primary endpoint measured in the LLNA is:

• Increased transepidermal water loss (TEWL)
• Proliferation of draining lymph node lymphocytes, measured by 3H‑thymidine or BrdU incorporation
• Histological epidermal thickness
• Percent peptide depletion in an in chemico assay

Correct Answer: Proliferation of draining lymph node lymphocytes, measured by 3H‑thymidine or BrdU incorporation

Q9. Which test is categorized as an in chemico assay within the defined approaches for skin sensitization?

• KeratinoSens
• h-CLAT
• DPRA (Direct Peptide Reactivity Assay)
• LLNA

Correct Answer: DPRA (Direct Peptide Reactivity Assay)

Q10. The Draize test is traditionally used to assess which dermal endpoint?

• Systemic immunotoxicity following dermal exposure
• Skin irritation and corrosion
• Covalent binding to keratin peptides
• Adverse outcome pathway mapping

Correct Answer: Skin irritation and corrosion

Q11. In LLNA data interpretation, a stimulation index (SI) of which value is generally considered a positive indication of sensitization?

• SI < 1
• SI = 1.5
• SI ≥ 3
• SI ≥ 10

Correct Answer: SI ≥ 3

Q12. The h-CLAT assay evaluates sensitization potential by measuring increased surface expression of which markers on THP‑1 cells?

• CD4 and CD8
• CD86 and CD54
• CK10 and filaggrin
• MHC class I and II only

Correct Answer: CD86 and CD54

Q13. Reconstructed human epidermis (RHE) models used for dermal irritation testing are primarily composed of:

• Immortalized fibroblasts only
• Primary or immortalized human keratinocytes forming a stratified epidermis
• Bacterial biofilms to mimic microbiome effects
• Mouse epidermal cells cultured on collagen

Correct Answer: Primary or immortalized human keratinocytes forming a stratified epidermis

Q14. Which assay is the standard in vitro test for assessing phototoxic potential of chemicals and formulations?

• 3T3 Neutral Red Uptake (NRU) phototoxicity test
• KeratinoSens photostability assay
• DPRA under UV exposure
• LLNA with UVA irradiation

Correct Answer: 3T3 Neutral Red Uptake (NRU) phototoxicity test

Q15. Which of the following is NOT considered a key event in the adverse outcome pathway (AOP) for skin sensitization?

• Covalent binding of electrophiles to skin proteins (Molecular Initiating Event)
• Keratinocyte activation and inflammatory mediator release
• Dendritic cell activation and migration to lymph nodes
• Melanocyte proliferation leading to pigment deposition

Correct Answer: Melanocyte proliferation leading to pigment deposition

Q16. How is dermal LD50 conventionally expressed in toxicology reports?

• mg per square centimeter of skin
• mg per kg body weight
• ppm in air
• Percent skin coverage

Correct Answer: mg per kg body weight

Q17. What is the primary purpose of tape‑stripping in percutaneous absorption or sensitization studies?

• Introduce allergens into the dermis directly
• Sequential removal of stratum corneum layers to study barrier function or enhance/test penetration
• Measure systemic blood levels of topically applied compounds
• Sterilize skin samples before in vitro testing

Correct Answer: Sequential removal of stratum corneum layers to study barrier function or enhance/test penetration

Q18. The cumulative irritancy test is designed to identify which property of a topical substance?

• Immediate hypersensitivity on single contact
• Ability to cause irritation after repeated, often sub‑threshold exposures
• Phototoxicity under UVA/UVB exposure
• Systemic toxicity following dermal administration

Correct Answer: Ability to cause irritation after repeated, often sub‑threshold exposures

Q19. OECD Test Guideline 442D corresponds to which in vitro method for skin sensitization testing?

• DPRA (Direct Peptide Reactivity Assay)
• KeratinoSens assay
• h-CLAT (human Cell Line Activation Test)
• LLNA (Local Lymph Node Assay)

Correct Answer: KeratinoSens assay

Q20. In the Guinea Pig Maximization Test (Magnusson & Kligman), which adjuvant is commonly used to enhance induction responses?

• Aluminum hydroxide gel
• Freund’s Complete Adjuvant (FCA)
• Polyethylene glycol (PEG)
• Sodium lauryl sulfate only

Correct Answer: Freund’s Complete Adjuvant (FCA)

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