By measuring the absolute weight and growth index of the bursa of Fabricius and using routine H.E method,the growth and histological development of the bursa in 1 to 49 days duckling were studied.The results showed that the absolute weight of the bursa increased as the ducklings grew.The growth index of the bursa reached its peak at 21 days.The height and width of both the large plica and projection formed by the follicle-associated epithelium(FAE)enlarged gradually,the same as the lymphoid follicle area and cortex width.The results indicated that the bursa of Fabricius in duckling develops slowly from 1 to 14 days,and quickly from 14 to 35 days(especially from 21 to 28 days),then steadily from 35 to 49 days.Histologically,the duckling bursa has approached its maturation by the 28th day.

Objective To construct chimerical DNA vaccine plasmid of human papiUomavirus type 11 (HPV11) L1-E7, and to evaluate its immunogenicity. Methods Molecular cloning techniques were used to construct recombinant plasmid PeDNA3 L1-E7 as a DNA vaccine. BALB/c mice were vaccinated with DNA recombinants through muscle injection. IL-2 and γ-INF secreted by immunized spleens lymphocyte and HPV 11 LI or E7 specific antibodies were assayed by ELISA method. Spleens lymphocyte proliferation was measured by MTT assay. Results The chimerical DNA plasmid of pcDNA3 LI-E7 was constructed correctly. Specific anti-HPV11 E7 and L1 antibodies, specific lymphocyte proliferation and secretions of IL-2 and γ-INF were detected in vaccinated mice. Conclusion Specific immune response, including cellular immunity and humoral immunity, could been detected in mice vaccinated with chimerical DNA vaccine of pcDNA3 L1-E7.