Effects of cadmium on catfish, Ictalurus melas, humoralimmune response

Catfish (I. melas) were exposed to 10, 20 or 30 μg 1−1 of cadmium (CdCl2) toassess its in vivo effects on the humoral immune response. After one week of cadmium exposure, the titer of total non-specific immunoglobulins was remarkably reduced but, after 2 weeks of exposure the IgM titer increased, and no differences between treated and control fish could be observed. Immunization of catfish with sheep red blood cells (SRBC) was also performed to assess the effect of cadmium on the immune response to a specific antigen. Fish exposed to cadmium (20 μg 1−1) required a shorter period to reach the peak of IgM anti-SRBC titer; moreover, fish exposed to Cd for 2 weeks before immunization reached peak antibody response more quickly and also revealed a remarkable increase in antibody titer.