Guinea Pig Maximization Test (Magnusson-Kligman)

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Objective:

To determine the sensitizing potential of a test article when applied dermally. This study has been modelled after the work of Magnusson, B. & Kligman, A. M., Journal of Investigative Dermatology, 52, p. 268, 1969, and complies with the standards set forth in OECD Guideline 406 and and EPA-OCSPP 870.2600

Principle:

Contact dermal sensitization is an immunological process where the host animal, through repeated skin exposure, acquires a specific allergic sensitivity to a substance. In the Guinea Pig Maximization (GPMT) model, contact dermal sensitivity is manifested as increased erythema.

Study Overview:

  • Typical Testing Duration: Approximately 10 weeks consisting of Pre-Test, Main Test and Reporting Periods.
  • Induction Phase: The first induction consists of multiple intradermal injections to the Test Group (20 animals). An adjuvant (50% Freund's Complete Adjuvant; FCA), the test article (TA) and a mixture of FCA and the TA are administered to the dorsum (clipped free of hair) in duplicate 0.1-ml injections. The TA concentration selected will not produce local necrosis or ulceration and be free of systemic toxicity.* Ten Vehicle Group animals are treated similarly, except replacing vehicle for the TA. The treated sites of each animal will be examined and scored at 24 and 48 hours after injection. Seven days later, the second induction is applied administered topically by applying a TA-saturated 2-cm x 4-cm section of Whatman No. 1 filter paper over the previously injected intradermal sites (clipped free of hair) for 48 hours as an occluded exposure. The TA concentration will be well tolerated systematically and will be the highest concentration to cause mild to moderate skin irritation.* The animals in the Vehicle Group will be treated in the same manner, but with the vehicle. The treated sites of each animal will be examined and scored at 48 hours after patch application.
  • Challenge Phase: Fourteen days after the topical induction, the animals in both the TA and Vehicle Groups are challenged topically over a 24-hour, occluded exposure, by applying a 2-cm x 2-cm section of Whatman No. 1 filter paper saturated with the highest non-irritating concentration* of the TA on the left flank. The vehicle is applied in the same manner as the TA and the patch is applied to the right flank of each animal. Challenge sites are scored 24 and 48 hours after patch removal.
  • Intepretation: In the GPMT, a score of 1 or greater for redness is considered a positive reaction. Sensitization potential is determined based on the percentage of animals showing a positive response.

*A six-animal screening study is required to determine the appropriate induction (intradermal and topical) and challenge (topical) concentrations.

What are In Vivo Sensitization Tests?

Test methods designed to identify substances with skin sensitization potential or cause allergic contact dermatitis, which is an important element in evaluating toxicity. Below are the available in vivo tests for dermal sensitization available: