感染传染性法氏囊病毒雏鸡的免疫抑制及其机理

本实验共用412只滨白雏鸡,分别在1日龄或4周龄时感染 IBDV,检测了雏鸡感染后其外周血液、泪液、气管液、肠液、胆汁中 IgG,IgM 和 IgA 含量、血液 T 细胞免疫功能和脾脏 B 细胞抗体生成功能、血液 T,B 细胞、淋肥细胞数量以及法氏囊、胸腺、脾脏、盲肠扁桃体、丕氏斑、十二指肠、哈德尔腺、支气管粘膜中浆细胞和酸性α-萘酚酯酶阳性 T 细胞(ANAE+T)数量的动态变化,结果如下:(1)雏鸡感染 IBDV 后,法氏囊、脾脏的浆细胞明显减少,脾脏 B 细胞抗体生成功能降低;胸腺、法氏囊、脾脏的 ANAE+T 细胞数量显著下降,说明感染鸡免疫器官的体液免疫功能和细胞免疫功能显著减弱.(2)IBDV 感染雏鸡引起呼吸道和消化道局部免疫组织一哈德尔腺、支气管粘膜、盲肠扁桃体、十二指肠粘膜固有层,丕氏斑的浆细胞和 ANAE+T 细胞较对照鸡显著减少;泪液、气管液、胆汁、肠液中 IgG,IgA,IgM 含量明显下降,表明感染鸡呼吸道和消化道局部的细胞免疫和体液免疫水平均显著降低.(3)感染鸡外周血液 T,B 细胞数量减少,T 细胞功能降低,IgG,IgA,IgM 含量明显下降,表明和标志全身体液免疫和细胞免疫水平降低,是免疫器官细胞免疫和体液免疫功能显著降低的反映和表现.(4)1日龄雏鸡感染 IBDV 后,B 细胞功能抑制时间明显长于 T 细胞,证明感染鸡 B 细胞功能的损害重于 T 细胞.(5)4周龄雏鸡感染 IBDV 引起的免疫抑制程度低于1日龄感染鸡,呈现一定的感染日龄差异.

MECHANISM OF IMMUNOSUPPRESSION IN CHICKENS INFECTED WITH INFECTIOUS BURSAL DISEASE VIRUS

Chickens were experimentally infected with IBDV at one day or 4 weeks old.At different ages of postinfection,the tear,trachea washings,intestinal fluids,blood and spleen of infected chickens were collected to detect the changes of the quantities of IgG,IgA,IgM,the immune function of T cell and the numbers of T cells,B cells and lymphocytes along with antibody producing function of splenocytes, respectively.The changes of the numbers of plasmacytes and Acid α-naphthyl acetate esterase positive T cells(ANAT+T)were determined in the Bursa Fabricius, thymus,spleen,cecal tonsil.duodenum,Peyer's patch,Harder gland and bronchus. The results are as follows. In the Bursa Fabricius,spleen and thymus of the infected chickens,the numbers of plasmacytes and ANAE+T cells were significantly lower than those of the control birds,except for plasmacytes in thymus.The antibody producing function of B cells dramatically declined in the spleen of the infected chickens in comparison with the control chickens.This indicated that the humoral and cellular immune functions were significantly suppressed in the immune organs of the infected chickens. The infection of chickens led to the marked reduction of plasmacytes and ANAE+T cells in the Harder gland,bronchus,cecal tonsil,Peyer's patch and duodenum;the contents of IgG,IgM and IgA significantly dropped in the tear, trachea washings,bile and intestinal fluids of infected chickens.This suggested that both the humoral and cellular immune functions of the infected chickens were markedly depressed in the local lymphoid tissues of alimentary and respiratory tracts.There were also a significant decrease of the number of T,B cells and lymphocytes,and a decline of the immune funetion of T cells as a well as a marked drop of IgG,IgM and IgA in the blood of the infected chickens.This demonstrated that there was significant suppression of systemic humoral and cellular immune functions of the infected chickens,which was the results of marked depression of immune functions in the immune organs of the the infected chickens. It was found that the suppression of immune function of B cells persisted for a longer period than that of T cells of chickens infected at one day old.This showed that IBDV infection caused severer damage to the function of B cells than that of T cells.The experimental results also indicated that the immunosuppression in the one-day-old infected chickens was far severer than in the four-week-old infected chickens,and that the IBDV infection had different immunosuppression effects on chickens of different ages.