Morphological Study On The Development Of Chicken Thymus

Thymus is a kind of central lymphoid tissue in which bone marrow-derived cells differentiate and mature into immunocompetent T cells. T cell has its cellular immune function to protect organism. The animal thymus existence age-associated thymicatrophy, organism also along with it senile and disease. The mechanism and principle of changes characteristic of thymic involution is not clear till now. Therefore, the present study took chicken as objects to study structural feature, neuroendocrine and immune character to investigate the underlying mechanism of neuroendocrine-immune network function in thymic development and ageing.The main researches and results were as follows:1 The anatomical and histologic structure of chicken thymus at different periodsObjective:To explore the morphologic changes of the structurally atrophied thymus in chicken with age and its possible mechanism of thymus involution. Methods:The thymus were embedded with parafin and stained with hematoxylin and eosin, PAS. And morphology target of structure changes of the thymus were determined. Results:The chicken thymus is enclosed by a thin connective tissue capsule that penetrates the parenchyma and divided it into many thymic lobule:As expected, each lobule consisted of a peripheral, darkly staining lymphocyte-rich cortex and an inner, paler medulla containing more epithelial cells, a small quantity of lymphocytes and typical Hassall's corpuscles (HC). With age increasing, the cortex area become thinner, thymic atrophy is marked by a decrease in the ratio of cortex to medulla and changes in thymocyte subset composition, suggesting alterations in the T-cell differentiation/maturation pattern. abundance of blood vessels become higher, and the number of typical Hassall's corpuscles (HC), expression of thymic involution, show a mild trend to increase from 1 day to day 21, and decrease from day 35 to day 120, calcific Hassall's corpuscle (HC) while cystiform Hassall's corpuscle show a significant trend to increase. Conclusion: With age increasing,the diminishing ability of migration, development and differentiation of T cell from bone marrow contribute to decreased thymocytes and cortex area; the decreased thymocytes could not satisfied organism may result in compensatory increase of blood vessel, besides, thymus atrophy may also result in the increased number of blood vessel with fixed range; Hassall's corpuscle's function of secrete polysaccharides decreased relatively suggest that HC may be associated with thymic involution.2 The distribution and expressive intension of 5-HT in chicken thymus at different periodsObjective:To examin the distribution and expressive intension of 5-HT in chicken thymus with different ages. Methods:The immunohistochemistry SABC staining was used. Results:Intensely stained 5-HT cells were readily detectable in the chicken thymus at all ages tested. Groups of immunopositive cells were distributed in corticomedullary border and medullary. As a consequence, Histochemicial staining for cluster of 5-HT cells showed brown precipitates around the vessel walls that provide the blood supply to the thymus, there were also some diffused distribution of 5-HT positive cells. In addition,5-HT activity appears restrict around a calcific Hassall's corpuscle (HC) and shows a mildly positive reaction in typical Hassall's corpuscle. Upon high power magnification, it became clear that the 5-HT cells constitute a population of cells with diverse morphologies. While the majority of cells display a simple round to oval shape, some cells possess very conspicuous extensions. Conclusion:the predominant distribution in medullary of 5-HT may participate in the differentiation and maturation of T cells and regulation of blood supply to thymus; with aging, the cortex area became thinner,while the expressive intension of 5-HT were increased, may suggest that the low expression of 5-HT can promote the thymus growth, while high expression of 5-HT may contribute to thymic atrophy.3 The distribution and expressive intension of TLR4 in chicken thymus at different periodsObjective:To examin the distribution and expressive intension of TLR4 in chicken thymus with different ages. Methods:The immunohistochemistry SABC staining was used. Results:Intensely stained TLR4+ cells were readily detectable in the chicken thymus at early ages tested. Counterstaining with hematoxylin-eosin showed that the ring of TLR4 cells was located at the medullary side of the cortico-medullary border,which expressed on cells adjacent to Hassall's corpuscles and blood vessels,was conspicuously localized in the medullary regions but not in cortical area. Upon high power magnification, it became clear that the the overall staining characteristics of the TLR4 cells constitute a population of cells with diverse morphologies. The majority of cells display a simple round to oval shape, while some cells possess stellate appearance or very conspicuous extensions. expressive intension of TLR4 cells increased gradually from postnatal day 1 and peaked on day 35; then decreased gradually with ageing. Conclusion:The regular expression of TLR4 in chicken thymus indicate that TLR4 might play a role T cell development, differentiation and maturation; the temporal correlation between expressive intension of TLR4 and thymus development also suggests that the decreased expression of TLR4 might contribute to thymus involution and immunosenescence.