| Ostrich originated from African desert. A short intensive cultural history comparedwith fowl, cattle, pig and equus animals, big body configuration and extensive territory,all these factors cause ostrich disease research work developed inconveniently. Theostrich disease studies are still imperfect, not as profound as other animals in diseaseprevention and control. New castle disease (ND) is one of the most serious infectiondiseases that damage ostrich cultivation. The highest disease incidence of ostrich chicks is50%, the grown-up ostrich is 3%～6%. Often activating outdoors, ostrich inevitablycontacts with other wild birds or fowls, and cross infection of NDV between ostrich andother animals may be happened. In this research, ostrich chicks were divided intochallenge and control groups at random. Using the methods of transmission electronmicroscopy, radioactive immunoassay, histochemical method, immunohistochemistry andterminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), thestructural characteristics of ostrich chicks' immune organs and the role of immunologiccell, neuroimmunomodulation and apoptosis in the immune reaction after artificiallychallenged with chicken NDV were illustrated. The main research results are as follows:1. Morphological characteristics of ostrich chicks' immune organs8-weeks-old healthy ostrich chicks were selected from control group. The structuralcharacteristics of ostrich chicks' immune organs was detail observed using transmissionelectron microscopy, histochemical methods (Feulgen-Methylene blue staining andreforming Weigert staining) and HE staining. The results indicated the number of thymusis little, distributed the back of neck along two sides and clustered together. There weretypical Hassall corpuscles in the medulla of thymus. The cloacal bursa structured thehanging and lateral walls of cloaca, enveloped the cloaca and did not form the trulyindependent bursa. There densely distributed convex papilates on the surface of foldsinside bursa, with one bursa nodule in lamina propria of each convex papilate. There weremany round or ellipse structures, similar to ellipsoid, in the parenchyma of spleen. Thehomogeneous texture between ellipsoid analog and circum-lymph tissue was acidophiliamaterial, which were collagen fibers by specific staining and transmission electron microscopy. And it was not found in other animals. These results demonstrate there areobvious differences in the immune organs between ostrich chicks and other poultries.2. The immunological regulation function of immunologic cell in the defencereaction to counteract chicken NDVThe experimental animals were divided into challenge and control groups at random.The histochemical methods, Feulgen-Methylene blue staining and reforming Weigertstaining were used to study the plasma cell (PC) and mast cell (MC) in immune organs ofostrich chicks. The results are as follows:(1) In spleen the PCs were mainly in the medulla. The PCs in thymus distributedintensively and the number of it was most in cortex and the boundary of cortex andmedulla. The PCs in cloacal bursa were scattered in the whole bursa nodules. Afterartificially infected with chicken NDV within 1～7days, the number of PCs in spleen ofchallenge group reduced significantly compared with control group. The PCs in thethymic medulla decreased sharply at 3 days after challenged, reached minimum at 5 days(P＜0.01), then increased again. The amount of PCs in cloacal bursa reduced first, thencame back, and was equivalent to that of PCs in control group at 9 days. Those indicatePCs in immune organs are multitude and distribute widely. The number of PCs inimmune organs after artificially infected with chicken NDV is obviously less than that ofPCs in control group, as induces the loss of antibody formation and secretion, and inhibitsthe humoral immunoresponse.(2) The MCs in thymus distributed intensively and the number of it was most inmedulla and the boundary of cortex and medulla. In cloacal bursa the MCs were mainlyin the mucosa epithelium. The MCs in spleen were mainly intensively distributed in thesuperficial lamella of parenchyma. The kytoplasm of MC in thymus and cloacal bursacontained prunosus granula, while MC in spleen was stained amethyst. The shape,sizeand gray varies of MC were different in different location of the same organ. Afterartificially infected with chicken NDV, there was a decreasing trend of the number ofMCs in spleen. The MCs in thymus of challenge group, as well as in cloacal bursa, weresignificantly fewer than that of control group at 3 days. The results show the MC inimmune organs of ostrich chicks has heterogeneity. The dynamic changes of MC indicate that MC plays a marked role in the defence reaction and immunomodulation during theartificial infection with chicken NDV.3. Effect on neuroimmunomodulation after artificially infected with chicken NDVThe study was on the distribution of 5-HT immunoreactivity (5-HTir) positive cellsin immune organs of ostrich chicks, the dynamic changes on the expression of 5-HT andthe level of IL-2 in serum after artificially infected with chicken NDV, usingimmunohistochemistry, SABC, and radioactive immunoassay. The results showed the5-HTir positive cells in spleen intensively located in red pulp, and the expression ofpositive products was stronger. In thymus the 5-HTir positive cells mainly distributed theperiphery of blood vessel and the connective tissue in lobule of thymus. The 5-HTirpositive cells in cloacal bursa were scattered in the medulla of bursa nodules. Duringinfection, the amount of 5-HTir positive cells in spleen decreased sharply and wassignificantly lower than that of control group. And the expression of positive productsweakened. While there was an increasing trend of the number of 5-HTir positive cells inthymus, the expression of positive products strengthened. The 5-HTir positive cells incloacal bursa reduced at the early stage of the artificial infection, and began increasingagain. The level of IL-2 in serum slightly decreased at 1 day after challenged then cameback, but it was still significantly different compared with control group. All the datasuggest that the spleen is the important location where the peripheral 5-HT produced inimmune organs. The dynamic changes of 5-HTir positive cells indicate that 5-HTparticipate the nosogenesis of ND. The quantity and expression of 5-HTir is relevant topathological changes. IL-2 plays the important role in the immune response to counteractchicken NDV. The level of IL-2 in serum of challenge group correlates closely with thedamage of organism and the development of disease.4. The effect of chicken NDV on apoptosis in immune organs and central nervoussystem of ostrich chicksThe TUNEL was used to detect the apoptosis of nervous cells in central nervoussystem and lymph cells in immune organs of challenge and control group. The data bystatistical analysis showed the apoptosis in immune organs of challenge group obviouslyincreased during the first stage, then delined. In spleen the apoptosis increased significantly within 5～7 days after infection compared with control group. In thymus thenumber of apoptosis increased significantly at 1 day after challenged, and was alwayshigher than that of control group. The apoptosis of lymph cell in cloacal bursa increasedsignificantly within 1～7 days, besides, a great quantity of apoptosis of mucosaendothelial cells. In cerebellum the apoptosis of nerve cell mainly occurred in thegranular cells of granular layer. The number of the apoptosis in cerebellum of ostrichchicks, as well as that of the cerebral cortex and white matter of spinal cord, increasedsignificantly after artificially infected with chicken NDV. And the positive products ofTUNEL also took place in Purkinje cells of challenge group. The results elucidate thatchicken NDV can induce the apoptosis of nervous cells in central nervous system andlymph cells in immune organs of ostrich chicks. A large number of apoptosis of mucosaendothelial cells after challenged indicates it maybe participate the pathological changesof mucosa immunologic barrier. The apoptosis of nerve cell in brain has regioselectivity.
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