The effects of copper deficiency on human lymphoid and myeloid cells: an in vitro model

Cu has long been known to influence immune responses. An in vitro model system was established in which human myeloid (HL-60), B-lymphoid (Raji) and T-lymphoid (Molt-3) cell lines could be grown in culture media of varying Cu levels. Initially Cu was removed from the medium by dialysis of fetal calf serum against a metal-ion chelator, minor depletion of other trace metals being obviated by repletion with appropriate metal salts. The growth rate of HL-60 was significantly (P < 0.05) inhibited by 72 h Cu depletion. Molt-3 cells required a longer period, up to 144 h, in Cu-depleted medium before growth was impaired. Raji-cell growth was not affected. These results confirmed clinical observations that T-cell functions were more sensitive to Cu deprivation than B cells. Analysis of intracellular metal levels in Molt-3 cells showed that Cu levels had been significantly lowered (P < 0.05) although Ca2+ levels were raised. Intracellular activity of the antioxidant enzyme superoxide dismutase (EC 1.15.1.1) was significantly impaired (P < 0.05) in Molt-3 cells grown in Cu-depleted medium. Activity of the mitochondrial enzyme cytochrome c oxidase (EC 1.9.3.1) was also significantly impaired (P < 0.05) by Cu depletion. Each of these findings indicates an increase in the potential for cellular damage by reduced antioxidant activity, impairment of normal mitochondrial activity and excessive Ca2+ influx. A major consequence of the type of damage occurring under these circumstances is membrane disruption. This was confirmed by scanning electron microscopy of Molt-3 cells grown under varying Cu levels.