To assess the influence of rhLF expressed by mammary gland bioreactor of transgenic cows on immune function of rat offsprings.Methods According to the extended one-generation reproductive toxicity study protocol (OECD443), the experiment was divided into two groups, including control group and rhLF group. Diets containing 20% casein or recombinant human lactoferrin (rhLF) were fed to parental rats for 14 days prior mating and throughout pregnancy and lactation. Offsprings were randomly selected from each group and fed with corresponding diets from weaning to execution. Immune function of offsprings was assessed on PND0, PND21 and PND56. Results No significant differences were observed on hematology and percentage of lymphocyte subsets between various groups. PFC, the lymphocyte proliferative response and NK cell activity had no statistical difference(P＞0.05).Conclusion The results suggested that recombinant human lactoferrin exerts no adverse effect on the immune system of rat offsprings.