• Melissa M Camouse, Alan R Swick, Cindy A Ryan, Ben Hulette, Frank Gerberick, Sally S Tinkle, Susan T Nedorost, Kein D Cooper, Seth R Stevens, and Elma D Baron.
• University Hospitals of Cleveland/Case Medical Center, Cleveland, OH, USA.
• Dermatitis. 2008 Mar 1; 19 (2): 95-9.

BackgroundSquaric acid dibutyl ester (SADBE) is a known contact sensitizer, but dose-response data are not defined.ObjectiveTo determine the relationship between sensitization dose and contact hypersensitivity (CHS) response to SADBE in human volunteers. The study also aimed to investigate whether SADBE-reactive blood T cells could be detected using ex vivo mature dendritic cells (DCs) as antigen-presenting cells.MethodForty healthy volunteers were sensitized to either 12.5, 25, 50, or 250 microg of SADBE in a 48 microL volume. This was followed by elicitation 2 weeks later with five doses (0, 0.2, 2, 20, and 200 microg in 20 microL). An additional 10 subjects received the elicitation doses without prior sensitization. Blood samples obtained after sensitization were purified into T cells and mature DCs.ResultsA direct relationship between sensitization dose and in vivo CHS response was observed. The SADBE dose that effectively sensitized 50% of the population (ED50) was 22 microg/cm2. Significant SADBE-specific T-cell proliferation in vitro was not observed 2 weeks after sensitization but became evident after elicitation.ConclusionThis study establishes the in vivo dose-response characteristics of immune reactivity to SADBE and antigen-specific T-cell reactivity.

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