Allergic contact dermatitis

DERMATOLOGY

Dermatological diseases represent a major health problem due to the substantial patient population that is affected. Psoriasis, Allergic Contact Dermatitis (ACD) and Atopical Dermatitis (Allergic or Irritant Contact Dermatitis) are the major skin diseases of immunological origin.

Allergic contact dermatitis

> ACD is a delayed type of allergy that arises as a result of two essential stages:
      - Induction phase (sensitization of the immune system for an allergic response)
      - Elicitation phase (triggering of the response of the immune system)
Contact allergens are essentially soluble haptens (low molecular weight, easily cross the stratum corneum of the skin)


> ACD is a T-cell-mediated inflammatory reaction, characterized by the presence of:
      - Rash or skin lesions at the site of exposure (that can become raw, scaled or thickened)
      - Delayed appearance a day or two after exposure to the allergen
      - Confined to the area where the allergen touched the skin
      - Other symptoms may include itching, skin redness or inflammation, localized swelling and the area may become more tender or warmer

Allergic Contact Dermatitis in swine

The structure and the morphology of young pig skin is very similar to that of the human skin. In addition, contrary to rodents, pigs react for the same molecules and the same intensity like humans.

Based on the published experimental design (Mollison K. et al. 1999), the animals are sensitized with the contact allergen DNFB and challenged with the cross-reactive contact allergen DNCB. The read-out of the ACD reaction is carried out 24h after the challenge by visual scoring of erythema, edema and induration. This model allows the evaluation of topical glucocorticoids and other topical anti-inflammatory compounds.

Dose-response with DNCB

Non-sensitized pig

DNCB does not induces an inflammatory reaction (data not shown)

DNCB-sensitized pig

DNCB induces a dose-dependent inflammatory reaction →

The inflammatory reaction in the sensitized animals represents a pure ACD reaction which is not compromised by an unspecific (not T-cell mediated) irritative reaction.

Reversal of DNCB-induced reaction by clobetasol

The topical application of clobetasol (0.05% ointment) attenuates the ACD reaction.