Effects of acute, low-dose UVB radiation on the induction of contact hypersensitivity to diphenylcyclopropenone in man.

Healthy volunteers (n = 14, age range 20-31 years, mean 23) were irradiated on the inside of the left forearm on four consecutive days with their individual minimal erythemal dose of ultraviolet B (UVB) prior to sensitization in the same skin area with a 2% solution of diphenylcyclopropenone (DPCP). The reaction patterns were compared with 14 alopecia areata patients (age range 16-69 years, mean 40) starting topical immunotherapy with DPCP, sensitized without prior UVB treatment. Primary allergic reactions occurred in ten volunteers and in four alopecia areata patients. Patch testing on the upper back with serial dilutions of DPCP (1% to 10(-8)%) showed minimal dermatitis-eliciting concentrations ranging from 1 to 10(-4)% (mean 0.19%) in the volunteers as compared with 10(-1) to 10(-8)% (mean 0.025%) in the alopecia areata patients. Two patterns were discernible within the volunteers with respect to the intensity of the primary allergic and elicitation reactions. Ten volunteers reacted in a similar way to the alopecia areata patients, whereas four probands demonstrated very high minimal dermatitis-eliciting concentrations and overall less severe reactions. The DPCP-specific T-cell response using blood macrophages and B lymphocytes as antigen-presenting cells was measured in an in vitro assay in two alopecia areata patients and two volunteers having similar skin reactions as well as in two volunteers with overall less severe skin reactions. B lymphocytes from the alopecia areata patients and the volunteers with similar skin reactions induced a significant DPCP-specific T-cell proliferation exceeding the responses obtained using macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)