Strain differences in cadmium-mediated suppression of lymphocyte proliferation in mice

Strain differences were investigated on the proliferative responses of splenic lymphocytes obtained from C3H/He, BALB/c, and DBA/2 mice that were treated with cadmium (Cd) for 5 days (0.5 or 1.0 mg Cd/kg/day, sc), and the results were compared with those of in vitro treatment of spleen cells with Cd. Following in vivo treatment, splenocytes from the C3H strain were significantly more susceptible to suppressive effects of Cd exposure on all indices for proliferative responses to mitogens (concanavalin A, phytohemagglutinin, and lipopolysaccharide) and allogeneic lymphocytes, while those from DBA and BALB strains were fairly resistant. Among the three strains, the highest Cd concentrations in plasma and spleen were obtained in the C3H strain with the lowest hepatic concentration of Cd. On the other hand, the Cd exposure hardly affected the splenic concentration of zinc in the C3H strain in contrast to its decrease in the others. When spleen cells obtained from normal mice were treated in vitro with Cd, the C3H strain was more resistant to the suppressive effect of Cd than the other strains. These results indicate that the mouse strain variations in Cd-mediated suppression of lymphocyte proliferation are not based on intrinsic lymphocyte sensitivities, but likely are due to differences in the metabolism of Cd, which is under genetic control.