MCQ – 88477

A 20-year-old man presents to his family physician for treatment of itching after exposure to poison ivy. The patient’s hands and arms appeared red and were covered with oozing blisters and crusts as shown in the image). Which of the following represents the most important step in the pathogenesis of the sensitization phase of injury in this patient?

Correct Answer � C Explanation

Correct answer :c

The condition described in question is Allergic contact dermatitis

Allergic contact dermatitis is a model of spongiotic dermatitis, a reaction pattern in which there is edema in the epidermis. In the initial 24 hours following reexposure to the offending plant (elicitation phase), numerous lymphocytes and macrophages accumulate about the superficial venular bed and extend into the epidermis.

The epidermal keratinocytes are partially separated by the edema fluid, creating a sponge like appearance (spongiosis). 

During the sensitization phase, low molecular weight haptens combine with carrier proteins at the cell membrane of Langerhans cells.

These inflammatory cells carry processed antigen through the lymphatics to regional lymph nodes and present it to CD4+ T lymphocytes.

Sensitized T cells then migrate back into the epidermis. Cytokine production leads to the accumulation of more T cells and macrophages and to epidermal cell injury.