Contact hypersensitivity to disodium hexachloroplatinate in mice

Complex platinum (Pt) compounds are known as occupational respiratory sensitizers whereas their role in skin exposure is unclear. In this study, both skin irritation and induction of contact hypersensitivity by halide Pt salts were characterized in mice. Repeated application of Na2[PtCl6] (5% in acetone) to both ears of naive BALB/c mice induced activation of the draining auricular lymph nodes. Flow cytometric analysis revealed a striking increase in the number of lymph node cells expressing proliferating cell nuclear antigen. In separate experiments, Na2[PtCl6] or acetone were applied only to the right ear of mice on 4-8 consecutive days and the animals were challenged on the left ear 6 days later. Ear thickness was determined before and 0.5, 24, 48, and 72 h after challenge with 0.5 or 2% Na2[PtCl6] or acetone. Maximal swelling of the left ear was recorded at 48 h in Pt-sensitized mice challenged with 2% Na2[PtCl6]. Furthermore, the concentration of Na2[PtCl6] required for sensitization caused an irritant reaction as demonstrated by significant swelling of the right ear. These data support the concept that both irritant and allergic contact dermatitis to halide Pt salts may occur in humans. Concerning skin exposure to halide Pt salts, Pt-induced irritant reactions resulting from an intrinsic adjuvant's activity of the compound could be a prerequisite for sensitization.