Impact of In ovo-Administered Lead and Testosterone on Developing Female Thymocytes

Abstract

The developing immune system is particularly sensitive to lead-induced immunotoxicity, but in some models, genders can differ in lead-induced immunotoxicity. Using an avian in ovo model of lead-induced T-helper disruption, the ability of in ovo administered lead and testosterone to alter thymocyte maturation among female embryos was investigated. On embryonic day (E) 8, Cornell K-strain embryos were given either testosterone (12.5 μg/egg in ethanol) or 15% ethanol in 100 μl volume. The groups then received either lead acetate (200 μg/egg) or sodium acetate (control) on E 12 of incubation. On E 20, thymocytes from 4–5 female embryos per group were analyzed by flow cytometry for cell surface markers CD3, CD4, CD8, TCR1, and TCR2. Lead alone did not induce any appreciable changes among the cell populations measured in this study. However, when testosterone treatment was followed by lead (testosterone + lead), there was a significant increase in CD4⁺CD8⁺ double-positive cells compared with either control or lead treatment groups. Testosterone, either by itself or in combination with lead, significantly reduced the percentage of cells with the CD4⁺CD8⁻ phenotype when compared to the lead alone group. No change was detected with respect to the CD4⁻CD8⁺, CD4⁻CD8⁻, TCR1⁺, and TCR2⁺ phenotypes following any treatment. Therefore, sex hormonal balance in early life appears to influence the manner in which the developing thymus responds to the heavy metal lead.