Inhibition of Rat Natural Killer Cell Function by Carcinogenic Nickel Compounds: Preventive Action of Manganese<xref ref-type="fn" rid="FN2">2</xref>

Abstract

The effects of carcinogenic nickel [(Ni) CAS: 7440-02-0] and Ni compounds on the natural killer (NK) cell activity of rat peripheral blood mononuclear cells (PBMCs) were studied. Rhabdomyosarcomas were locally induced by one im injection of Ni or Ni subsulfide [(Ni3S2) CAS: 12035-72-2] dust in the hind leg of WAG rats. A weakly tumorigenic dose of 5 mg Ni3S2 (tumor incidence, 2%) induced a transient decrease of PBMC NK activity against YAC-1 cells in vitro (from the 17th to the 23d wk after Ni3S2 inoculation), which could be restored by in vivo injections of partially purified rat fibroblastic interferon (IFN). Injection of 20 mg Ni (tumor incidence, 47.5%) produced a long-lasting depression of NK cell activity (from the 8th to the 23d wk). In vivo chronic IFN treatment of the Ni-injected rats neither restored NK cell activity nor affected the tumor incidence. However, NK cells of Ni-treated animals responded normally to IFN in vitro. Prospective analysis of individual NK cell responses showed that a persistent depression of basal NK cell activity was restricted to rats that subsequently developed a tumor. In these animals the time between carcinogen treatment and clinical detection of the primary tumor was positively correlated with the mean level of NK cell activity (3-4 determinations/rat). Admixture of manganese to Ni inhibited the development of tumors and also prevented the depression of NK cell activity produced by Ni alone. Noncarcinogenic Ni oxide stimulated NK cell activity. These results point out the possible involvement of NK cells in resistance to Ni-induced carcinogenesis.