Abstract: In order to evaluate the effects of chronic exposure to genetically modified (GM) maize expressing Bacillus
thuringiensis (Bt) toxins on immunity in rats, flow cytometry and liquid chip method were applied to detect immune cell
phenotypes in the peripheral blood and spleen and the expression levels of related cytokines in the serum of parental rats
and newly weaning offsprings. Feeds with non-transgenic maize or commercial maize were used as control in this study. As
compared to the control maize, Bt maize did not induced any alteration in the percentage of T and B cells and CD4+, CD8+,
TCR αβ+, and TCR γδ+ subpopulations either in blood and spleen of parental rats or in the spleen of weaning offspring.
No significant difference in the expression levels of cytokines (IL-4, IL-5, IL-6, IL-10, IL-12p70, IL-13, IFN-γ, TNF-α,
MCP-1β, and MIP-1α) in the serum of parental rats was observed between the Bt and parental control maize groups (P > 0.05).
However, the percentage of peripheral B cells was raised significantly, while the expression levels of MIP-1α, MCP-1β and
IL-5 were significantly decreased in the peripheral blood of weaning offspring (P < 0.05). These results suggest long-term
consumption of genetically modified maize does not affect the immune system of parental rats, but may exert some influence
on cellular and humoral immunity in weaning offspring.

Key words: transgenic maize, safety assessment, immunotoxicity, lymphocyte subpopulations, cytokines