106 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS exacerbated allergic contact dermatitis via the alteration of Ia+ epidermal immune cells. In the present study we were able to demonstrate that a short-term application of MBEH could significantly increase the density of Langerhans cells (1.4% to 3.3%) as well as the mean phenotypic expression of the Ia antigenic marker. Several investigators have reported that the increase in Ia q- antigen or analogue in man, HLA-DR, can be directly correlated with an intensified allergic contact dermatitis reaction. Further, our current studies examine more ubiquitous antioxidants, namely BHT and BHA, using an in vitro cell culture system. Results from these experiments strengthen our earlier findings that antioxidants can play a role in altering epidermal immune reactivity. Further, this reponse could be reproduced using a biologically relevant molecule, ara- chidonic acid. In summary, we have presented the results of experiments which demonstrate the use of FACS as a sensitive and precise tool to measure small yet significant identifiable changes in epidermal immune molecules residing in the epidermis. This technique, along with the use of human epidermal cell suspensions obtained from various sources (i.e., sur- gical specimens), theoretically provides one with a technique to determine which cos- metics and/or pharmaceutical formulations may alter the epidermal immune homeo- stasis, thereby potentially leading to exacerbated allergic contact dermatitis both in the home and in the workplace. ACKNOWLEDGMENTS This study was supported in part by NIH Grant AM25252, NIOSH Grant ROI OH02091, and the Elma Margaret Lapp Foundation, Cincinnati, Ohio. The authors are grateful to Ms. Catherine Goldschmidt for her assistance in the prepara- tion of the manuscript. REFERENCES (1) L. A. Rheins and J. j. Nordlund, Modulation of the population density of identifiable epidermal Langerhans cells associated with enhancement or suppression of cutaneous immune reactivity. J. Immunol., 136, 867-876 (1986). (2) L. A. Rheins, E. M. Young, M. L. Nordlund, R. B. Berning, and J. J. Nordlund, Rapid induction of Thy-1 antigenic markers on keratinocytes and epidermal immune cells in the skin of mice fol- lowing topical treatment with common preservatives used in topical medications and in foods, J. Invest. Dermatol., 87, 489-494 (1987). (3) C. A. Janeway, A. K. Bottomly, J. Babich, P. Conrad, S. Conzen, et al., Quantitative variation in Ia antigen expression plays a central role in immune regulation, Immunol. Today, 5, 99-104 (1984). (4) L. K. Roberts, G. G. Krueger, and R. A. Daynes, Correlation between the inducible keratinocyte expression of Ia and the movement of Langerhans cells into the epidermis, J. Immunol., 134, 3781-3784 (1985). (5) L. K. Roberts, G. J. Spangrude, R. A. Daynes, and G. G. Krueger, Correlation between keratino- cyte expression of Ia and the intensity and duration of contact hypersensitivity responses in mice, J. Immunol., 135, 2929-2936 (1985). (6) V. B. Morhenn, B. J. Nickoloff, and J. N. Mansbridge, Induction of the synthesis of Triton-soluble proteins in human keratinocytes by gamma interferon, J. Invest. Dermatol., 85, 27-29 (1985). (7) L. A. Rheins, L. Barnes, S. Amornsirpanitch, C. E. Collins, and J. J. Nordlund, Suppression of the

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