Different effects of platinum, palladium, and rhodium salts on lymphocyte proliferation and cytokine release

The effects of graded concentrations of Pt, Pd, and Rh salts on spontaneous and PHA-stimulated peripheral blood mononuclear cell (PBMC) proliferation and IFN-γ, TNF-α, and IL-5 release were the focus of this study. Spontaneous PBMC proliferation was inhibited by all 10-4 M salts (with the exception of PtCl2), while it was enhanced by 10-5 M PtCl2 as well as by 10-5 and 10-6 M (NH4)2[RhCl6] and RhCl3 (but not by 10-7 M salts). Pt, Pd, and Rh compounds showed similar effects on PHA-stimulated PBMC proliferation and cytokine release; however, the effects on IFN-γ release were stronger. Thus, 10-4 and 10-5 M (NH4)2[PtCl6] and 10-4 M (NH4)2[PtCl4] inhibited the PHA-stimulated immune activity;10-4 M PtCl2 did not exert activity, while10-6 M (NH4)2[PtCl6] and 10-5 and 10-6 M (NH4)2[PtCl4] and PtCl2 enhanced PBMC proliferation and/or cytokine release. (NH4)2[PdCl6] showed stronger dose-related inhibitory effects (present also at 10-7 M concentration) on PHA-stimulated proliferation and cytokine release than (NH4)2- [PdCl4], PdCl2, or Rh salts; the inhibitory activity of (NH4)2[RhCl6] was slightly higher than that of RhCl3. In conclusion, this study shows that: (a) the immune capacity of Pt, Pd, and Rh depends on speciation; (b) low concentrations of Pt salts stimulate spontaneous and PHA-stimulated immune responses; (c) the in vitro activity of Pd compounds (which are only inhibitory) is higher than that of Pt and Rh salts. These findings are consistent with the observations that sensitization and allergic contact dermatitis in response to Pd are increased in the general population, although the roles of cross-sensitization to Pd and Ni are difficult to determine.