Morphological Study On The Development Of Chicken Bursa Of Fabricius

Bursa of Fabricius (BF) a specific immune organ of the birds, is the spaces of B lymphocyte development, differentiation and maturation. B lymphocytes matured in the bursa of fabricius migrate to the peripheral lymphoid organs settling in and propagating to perform essential immune function. Young chickens bursa was vulnerable to be damaged, or even atrophy, causing immune suppression, which has brought huge economic losses in the poultry production.Therefore, the research on the regulation mechanism of the development of chicken bursa is very important to the prevention and diagnosis of chicken disease.This study was performed to investigate bursal morphological structure, bursal polysaccharide, mast cells and TLR4variation in different day-old chicken, to explore the mechanism of bursal development. The main contents and results are as follows:1The morphological developmental variation in chicken bursa of fabriciusThe HE staining technique was used to study the morphology structural characteristics in the different ages of chicken bursal. The results were as follows:With the growth of age, bursal constantly improve their own structure, cell arrangement more closely, lymphoid follicles gradually increased, Lymphocytes gradually increased,At1day old,4-5elongated mucosal folds formed in bursa, Submucosa was thin and had loose mesh. There is small number of smooth muscle cells in the muscular layer and the serosa was also the thin layer. At7day old, Bursal lymph nodes had clear boundaries of the medullary and cortical substance, the number of follicles had substantial increase, At21-day old to35-day old, follicular gradually transformed from a polygon into a rectangle. In42days, the epithelial cells gradually increased, closely distributed and the nucleus located on the bottom of the basal taking on a straight line. This result shows that, chicken bursal develop improved gradually with the growth of day-old.2The polysaccharide developmental variation of chicken bursa of fabriciusPAS staining technique was used to study polysaccharide material variation in the development of bursa of fabricius.The results were as follows:There was a large expressed polysaccharide substance in the bursa,mainly expressed in the mucous layer of epithelium and lamina propria, cortex and medulla are rarely distributed.With the growth of age, bursal mucosa positive cells is more obvious, especially in epithelium and lamina propria,and lymphoid nodules was less,The statistical results shows:Compared with other age groups, the area and optical density values of polysaccharides difference was significant at42days of age (P<0.05).This study shows that, bursa mucosa contains a crowd of polysaccharide possibly duing to mucous layer’s easy contact with the outside world. Consistently, the rapid metabolism, growth and proliferation of lymphocyte benefit in resisting external pathogenic microorganisms.3The mast cell developmental variation of chicken bursa of fabriciusToluidine blue staining technique was used to study the distribution and developmental of mast cells in the bursa of Fabricius. The results were as follows:Mast cells are abundantly expressed in the bursa, And mainly distributed in the mucosal epithelium and the connective tissue surrounding lymphoid follicles. With the growth of age, the expression of the mucous layer increases with age, There was gradually increasing trend, But in the lamina propria and submucosa, there was first increased and then decreased, mast cells embodied in the mucosal layer and there was no distribution in the cortex and medulla after21days.The statistical results show that, compared with other age groups, the number,area and optical density values of mast cells different was significantly at42days of age (P<0.05),This study shows that:the bursa mast cells mostly located in shallow beneath the epithelial, lamina propria or perivascular connective tissue and few mast cells distributed in the connective tissue of the submucosa. The muscle membrane and the serosa had slightly distribution.4The TLR4developmental variation of chicken bursa of fabriciusThis study was performed using immunohistochemical techniques to explore the TLR4distribution and development changes in the bursa of Fabricius. The results were as follows:TLR4are expressed within the entire bursa, Mainly distributed in the mucosa and submucosa, especially submucosal lymphoid nodules, With the growth of age, TLR4expression was first increased and then decreased in the bursa,Basically increased with age in1-35days, and then a significant downward trend at42days of age,The statistical results showed that, compared with other age groups, TLR4positive cells and optical density values different was significantly at35days of age(P<0.05),This study shows that: the immune factor TLR4showed regular pattern in the bursa of different ages, and the expression intensity also showed correlation with bursal development.This result gave the clue that natural immune factors of TLR4played a very important role in the early stage of growth and development in the bursa.