revised final - Agency for Toxic Substances and Disease Registry ...

MERCURY 123
2. HEALTH EFFECTS
Organic Mercury. No studies were located regarding other systemic effects in humans or animals after oral
exposure to organic mercury.
2.2.2.3 Immunological and Lymphoreticular Effects
Inorganic Mercury. No studies were located regarding immunological or lymphoreticular effects in
humans after oral exposure to inorganic mercury.
The immune response to mercury exposure is complex, depending in part on the dose of mercury and the
genetic characteristics of the exposed population (see Section 2.4). Administration of 14.8 mg Hg/kg/day
as mercuric chloride to B6C3F 1 mice 5 days a week for 2 weeks resulted in a decrease in thymus weight
(NTP 1993), suggesting immune suppression. However, a 2-week exposure to 0.7 mg Hg/kg/day as
mercuric chloride in the drinking water resulted in an increase in the lymphoproliferative response after
stimulation with T-cell mitogens in a strain of mice particularly sensitive to the autoimmune effects of
mercury (SJL/N) (Hultman and Johansson 1991). In contrast, a similar exposure of a strain of mice
(DBA/2) not predisposed to the autoimmune effects of mercury showed no increase in lymphocyte
proliferation.
A significant suppression of the lymphoproliferative response to T-cell mitogens, concanavalin A, and
phytohemagglutinin was observed in male B6C3F 1 mice administered 2.9 or 14.3 mg Hg/kg/day as
mercuric chloride in drinking water for 7 weeks (Dieter et al. 1983). A significant decrease in the weight of
the thymus and spleen and a decrease in antibody response were also exhibited at 14.3 mg Hg/kg/day. An
increase in B-cell-mediated lymphoproliferation was, however, observed at both 2.9 and
14.3 mg Hg/kg/day. No immunological effects were observed at the lowest dose of 0.57 mg Hg/kg/day.
When SJL/N mice were administered mercuric chloride in the drinking water for 10 weeks, an increase in
circulating antinucleolar antibodies was observed at 0.28 mg Hg/kg/day, and deposition of granular IgG
deposits was observed in the renal mesangium and glomerular blood vessels at 0.56 mg Hg/kg/day
(Hultman and Enestrom 1992).
In rats, immune deposits have been observed in the basement membrane of the intestines and kidneys
following gavage exposure to 2.2 mg Hg/kg/day as mercuric chloride twice weekly for 2 months, although
no functional changes were evident in these tissues (Andres 1984). The observation of these deposits
suggests that autoimmunity to specific components of these tissues has developed.