The efficiency of maternal transfer of lead and its influence on plasma IgE and splenic cellularity of mice

Exposure to the well known environmental toxicant lead is typically assesse d by blood and/or bone levels and has been implicated in the onset of a var iety of diseases affecting multiple human systems. However, there are confl icting data regarding the efficiency of in utero versus lactational transfe r of lead to offspring, and the immunomodulatory effects of lead in early l ife have not been well defined. Pregnant BALB/c mice were exposed to lead a cetate in their drinking water beginning at approximately day 15 of gestati on, and cross-fostering of exposed/nonexposed litters was performed at part urition. Significant increases of blood lead levels of all exposed offsprin g were found at 1 week of age with evidence for both transplacental and lac tational transfer. Additionally, mice exposed to lead continuously beginnin g at approximately 6 days prior to birth showed significant decreases in th eir blood lead levels 2 weeks after weaning, despite continued exposure as adults. This result suggests maternal transfer of lead is more efficient th an oral adult exposure and that substantial lead transfer occurs both trans placentally and lactationally. The incidence of childhood atopic responses including asthma has risen considerably in recent years, particularly withi n areas containing higher levels of environmental pollutants. Plasma IgE le vels of 2-week-old neonates exposed to lead before and/or after birth were measured as an index of atopy. Neonates exposed to lead transplacentally an d/or lactationally had significantly higher plasma IgE levels, a biomarker of atopy, and lower splenic white blood cell numbers than age-matched contr ols. These results resemble the lag in immuno-competency and increase in se rum IgE noted in atopic children and suggest a role for environmental toxic ants and non-allergen-specific immunology in the prevalence of atopy and as thma in children.