Flow cytometric analysis of regulatory T cells during hyposensitization of acquired allergic contact dermatitis

Background: We previously demonstrated that repeated intradermal steroid injections administered at weekly intervals into positive patch-test sites induce hyposensitization and desensitization. Objective: To examine changes in CD4⁺CD25⁺CD127lo/j regulatory T cells during the attenuation of the patch-test response. Methods: Ten patients with known allergic contact dermatitis were patch tested weekly for 10 weeks. The patch-test site was injected intradermally with 2 mg triamcinolone. At weeks 1 and 7, a biopsy was performed on the patch-test site in 6 patients, and flow cytometry was performed assessing CD4⁺CD25⁺CD127lo/j regulatory T cells. Secondary outcomes were clinical score, reaction size, erythema, and temperature. Statistical analysis included regression, correlation, and repeated-measures analysis of variance. Results: The percentage of CD4⁺CD25⁺CD127lo/j regulatory T cells, measured by flow cytometry, increased from week 1 to week 7 by an average of 19.2%. The average grade of patch-test reaction decreased from +++ (vesicular reaction) to ++ (palpable erythema). The mean drop in temperature following treatment was 0.28-C per week. The mean area decreased 8.6 mm²/wk over 10 weeks. Conclusions: Intradermal steroid injections of weekly patch-test reactions resulted in hyposensitization of the allergic contact dermatitis reaction. CD4⁺CD25⁺CD127lo/j regulatory T cells showed a tendency to increase; however, further studies are needed to determine if this is significant.