Comparisons Of Histological Structure Of The Lymph Node At Different Ages In Yak

Objects: Lymph node was an independent secondary immune organ,which located in the lymphatic circulation.The change of histological structure and function in lymph node was one of the key factors to resist external infection for body.As one of the most frequent pathology of the organization,the change of histological structure in lymph node provided the foundation to clinical diagnosis.Currently,the comparative study of the lymph node during its development,there was no reported both at home and abroad.Yak was a special cattle species,who lived in the high altitude and bad cold weather area.The immune and health of yaks played a vital role to deal with some natural stress such as hypoxia,cold and ultraviolet radiation.Methods: The experiments selected lymph node samples from different anatomical sites(i.e.mesenteric,hilar,iliac,mandibular)and age groups(i.e.newborn,half-year –old,one-year-old,adult and senility)of the yak,five copies of each carotid were sacrificed,quickly gathering fresh lymph.Lymph node samples immersed in 40 g / L paraformaldehyde phosphate buffer(p H 7.2 ~ 7.4)fixed one week.Using histological and immunochemical methods to observe the histological characteristics of the lymph node of yaks.Results:(1)The primary and secondary lymphoid follicles could be found in lymph nodes of newborn yaks,the distribution of reticular fibers in the medullary cord of newborn yak was loose,and there was no reticular fiber in the medullary sinus.In the other four age groups,the lymphoid follicles were mainly existed in secondary form,the distribution of reticular fibers in medullary cord was dense,and the reticular fibers crossed with medullary sinus.(2)In five age groups,the number of germinal centers per unit area and percentage of relative cortical area of lymph nodes in yak increased first and then decreased with along age,and reached the peak at the age of 1-year-old.In addition to the iliac lymph nodes,the remaining three parts of the relative medulla area of lymph node with age showed a downward trend,and reached a maximum at newborn.Conclusion: In this study,the changes of histological structure of lymph node of yak were analyzed in detail,and found that the germinal center in lymph nodes had been formed at the early postnatal period in yak.The changes of histological structure of lymph node were closely related to age.It was presumed that yak may have established immune adaptability to alpine hypoxia environment at early birth.