Elevated serum copper is associated with reduced immune response in aging mice

Young mice were found to have serum copper concentrations ranging from a low of 0.291 to a high of 0.584 ppm. Old mice had serum copper concentrations ranging from 0.223 to 1.715 with 30.9% of the old animals having values greater than 0.6 ppm. The mitogen response of isolated lymphocytes from the spleens of aging mice was greatly reduced when these cells were taken from animals with naturally occurring serum copper levels in excess of 0.6 ng of copper/mg wet weight serum. The lymphocytes taken from young mice with higher serum copper concentrations, on the other hand, had increased response to mitogens. Addition of the copper protein, ceruloplasmin, to lymphocyte cultures in vitro reduced the mitogen response of purified splenic lymphocytes with the reduction being greater for cells from old animals. We suggest that excess serum copper and ceruloplasmin may be immunosuppressive, especially in older organisms.