EFFECTS OF CADMIUM ON LYMPHOCYTE-PROLIFERATION AND MACROPHAGE ACTIVATION IN CATFISH, ICTALURUS-MELAS

The effects of cadmium (Cd) (in vitro and in vivo) on phytohaemoagglut inin(PHA)- or lipopolysaccharide(LPS)-induced lymphocyte proliferation were investigated in the catfish, Ictalurus melas. The effects of Cd on macrophage activation by Concanavallina A or Saccharomyces cerevisi ae, as measured by superoxide (O-2(-)) production, were investigated. Dose-independent (except at 2 mu M Cd) inhibition of T cell stimulatio n and dose-dependent inhibition of B cell stimulation, by lymphocytes exposed in vitro to 2-40 mu M Cd, was found. In vivo, 20 mu g l(-1) Cd inhibited both PHA- and LPS-induced lymphocyte proliferation, at 4 da ys of exposure and throughout the duration of the experiment. During t he first week of exposure, Cd significantly decreased spontaneous H-3- methyl-thymidine uptake from unstimulated lymphocytes; however, 15 day s after exposure unstimulated cells recovered their basal level of spo ntaneous thymidine uptake. In vitro 2-40 mu M Cd enhanced O-2(-) produ ction by activated macrophages, while the addition of 50-100 mu M Cd h ad no significant effects.