IMMUNOMODULATING EFFECTS AFTER PERINATAL EXPOSURE TO METHYLMERCURY INMICE

The influence of methylmercury on the developing immune system was stu died in offspring from Balb/c mice exposed to 0, 0.5 or 5 mg Hg/kg as methylmercury in the diet. Dams were exposed for 10 weeks prior to mat ing, during gestation and lactation. Pups were exposed to mercury unti l day 15 of lactation, thereafter the pups were given control milk and control diet. Samples for mercury analysis were collected from the pu ps on days 22 and 50, and for immunological studies on days 10, 22 and 50. The exposure resulted in significantly increased total Hg concent rations in whole blood on day 22 and 50 in offspring from the 5 mg Hg/ kg group, and in offspring from the 0.5 mg Hg/kg group on day 22. On d ay 50, blood mercury levels had decreased to background levels in the 0.5 mg Hg/kg group. Increased numbers of splenocytes and thymocytes we re found in offspring from the 0.5 mg Hg/kg group. Flow cytometry anal ysis of thymocytes revealed increased numbers and altered proportions of lymphocyte subpopulations within the thymus in offspring from both of the exposed groups. The proliferative response of splenocytes to th e B-cell mitogen LPS was increased in offspring from dams exposed to 5 mg Hg/kg, and the primary antibody response to a viral antigen was st imulated in pups from dams exposed to 0.5 mg Hg/kg. The present result s indicate that placental and lactational transfer of mercury affects thymocyte development and stimulates certain mitogen- or antigen-induc ed lymphocyte activities in mice.