Strontium 90 (90Sr) remains in the environment long after a
major nuclear disaster occurs. As a result, populations living on
contaminated land are potentially exposed to daily ingesting of low
quantities of 90Sr. The potential long-term health effects of
such chronic contamination are unknown. In this study, we used a mouse
model to evaluate the effects of 90Sr ingestion on the immune system, the animals were chronically exposed to 90Sr
in drinking water at a concentration of 20 kBq/l, for a daily ingestion
of 80–100 Bq/day. This resulted in a reduced number of CD19+
B lymphocytes in the bone marrow and spleen in steady-state conditions.
In contrast, the results from a vaccine experiment performed as a
functional test of the immune system showed that in response to
T-dependent antigens, there was a reduction in IgG specific to tetanus
toxin (TT), a balanced Th1/Th2 response inducer antigen, but not to
keyhole limpet hemocyanin (KLH), a strong Th2 response inducer antigen.
This was accompanied by a reduction in Th1 cells in the spleen,
consistent with the observed reduction in specific IgG concentration.
The precise mechanisms by which 90Sr acts on the immune system remain to be elucidated. However, our results suggest that 90Sr
ingestion may be responsible for some of the reported effects of
internal contamination on the immune system in civilian populations
exposed to the Chernobyl fallout.