Anatomical And Histological Structures And Dynamic Expression Of IgA,IgG,SIRP?and CD68 In Different Age Yak Palatine And Pharyngeal Tonsils

ObjectsThe tonsils are secondary lymphoid organs which form the waldeyer ring at the junction of the digestive and respiratory tracts and are typical mucosa-associated lymphoid tissues which have crypts and reticular epithelium.The palatine tonsils are the most representative structures of the oropharynx and form the sites of entry and replication for some pathogens.The pharyngeal tonsil is the most representative structure of the nasopharynx,and it is also an important part of the respiratory related lymphoid tissue.Functionally,the tonsils provide a significant part of the protective immunological ring at the openings of the digestive and respiratory tracts and play a key role in initiating immune responses against ingested antigens.This study using anatomical and histological techniques,qRT-PCR,WB,ELISA and immunohistochemistry methods,describes the anatomical and histological structures and dynamic expression of IgA,IgG,SIRP? and CD68 in different age groups of yak palatine and pharyngeal tonsils.These findings will add new information for comparative histology,at the same time provide the theoretical basis and experimental basis for the study of high altitude medicine and sports medicine.Materials and Methods1.Materials: Five healthy yaks in each group of newborn(1-7 days old),juvenile(5-7 months old),adult(2-6 years old)and aged(7-10 years old)were used.2.Methods: Anatomical,histological,immunohistochemistry and molecular biology techniques(qRT-PCR,WB and ELISA)were used to observe and detect the developmental changes of anatomical and histological structures and dynamic expression of IgA,IgG,SIRP? and CD68 in different age group of yak tonsils.Results1.The results of the study showed that there were five kinds of tonsils in yak which include the palatine tonsil,the tonsil of the soft palate,the lingual tonsil,the pharyngeal tonsil and the tubal tonsil.The palatine tonsil,the tonsil of the soft palate and the lingual tonsil were oropharynx tonsils.The stratified squamous epithelia covering them had a thick underlying layer of connective tissue,which invaginated into the connective tissue and formed crypts.In some places,the stratified epithelium of the crypt was infiltrated by non-epithelium cells forming reticular epithelium.In the three oropharyngeal tonsils,the paired palatine tonsils were the largest,resembling a kidney,the central depression formed a tonsil sinus.Some external crypts and internal crypts were present around the tonsil sinus.The lingual tonsil was the smallest.The pharyngeal tonsil and the tubal tonsil were nasopharynx tonsils.Their epithelium were predominantly pseudostratified columnar ciliary epithelium,in some places,the epithelium was also infiltrated by non-epithelium cells forming reticular epithelium.Their epithelium were covered by a thin underlying layer of connective tissue.In the two nasopharyngeal tonsils,the pharyngeal tonsil was the largest with a rough surface and the radiation was arranged in an umbrella shape.In yak,tonsils had crypts except the tubal tonsil.The number of crypts from high to low were the palatine tonsil,the pharyngeal tonsil,tonsil of the soft palate,the lingual tonsil and the tubal tonsil.In addition,there were well-developed primary and secondary lymphoid follicles in each tonsil and the trend of the number of lymphoid follicles was consistent with that of the crypts.2.In adult yak tonsils,both the IgA and IgG ASCs were distributed in the subepithelial lamina propria of the crypt stratified squamous epithelia and pseudostratified columnar ciliary epithelium,the reticular crypt epithelium,lymphoid follicles,interfollicular areas and around the glands.The distribution of CD68 and SIRP? was basically consistent in adult yak tonsils,they were distributed in the lymphoid follicles,interfollicular areas,excretory tube wall,glandular cells of serous glands and serous demilune and between glands.In the oropharynx tonsils,CD68 and SIRP? were distributed in the keratolytic layer of outer surface squamous epithelium,lamina propria,crypt epithelium and sometimes positive expression was seen in epithelial cells shed in the crypt lumen.In the nasopharynx tonsils,CD68 and SIRP? were distributed in the epithelium mucosa of the pseudostratified cilia columnar,lamina propria,reticular epithelial.The expression levels of IgA,IgG,SIRP? and CD68 mRNA and protein were different in the five kinds of tonsils of adult yaks,which from high to low were the pharyngeal tonsil,palatine tonsil,tonsil of the soft palate,lingual tonsil and tubal tonsil.3.The histological characteristics of yak palatine tonsils were that there were no lymphoid follicles observed in newborn group.In the other three groups,the lymphoid follicles consisted of primary and secondary lymphoid follicles.The number of lymphoid follicles gradually increased from newborn to adult and peaked in adulthood,but declined as the yak aged.In the different age group of yak palatine tonsils,both IgA and IgG ASCs were distributed in the subepithelial lamina propria of the crypt stratified squamous epithelia,the crypt reticular epithelium,lymphoid follicles,interfollicular areas and around the glands.The distribution of CD68 and SIRP? was basically consistent.They were distributed in the keratolytic layer of outer surface squamous epithelium,lamina propria,crypt epithelium and sometimes positive expression was seen in epithelial cells shed in the crypt lumen,lymphoid follicles,interfollicular area,excretory tube wall,glandular cells of serous glands and serous demilune and between glands.The expression trends of IgA,IgG,SIRP? and CD68 mRNA and protein in the palatine tonsils correlated with age and were also positively correlated with the trends in size of the palatine tonsils and the number of lymphoid follicles.4.The histological characteristics of yak pharyngeal tonsil had two points.One was that in newborn yaks,fully developed primary lymphoid follicles had been observed and the other was that in old yaks,the degenerate lymphoid follicles appeared.Consistent with the characteristics of the palatine tonsils,primary and secondary lymphoid follicles were observed in both juvenile and adult yak pharyngeal tonsils.The number of lymphoid follicles gradually increased from newborn to adult and peaked in adulthood,but declined in the old yak.In the different age group of yak pharyngeal tonsils,both IgA and IgG ASCs were located in the subepithelial lamina propria of the pseudostratified columnar ciliary epithelium,the reticular crypt epithelium,lymphoid follicles,interfollicular areas and around the glands.The distribution of CD68 and SIRP? were basically the same.They were distributed in the epithelium mucosa of the pseudostratified cilia columnar,lamina propria,crypt epithelium and sometimes positive expression was seen in epithelial cells shed in the crypt lumen,lymphoid follicles,interfollicular area,excretory tube wall,glandular cells of serous glands and serous demilune and between glands.The expression trends of IgA,IgG,SIRP? and CD68 mRNA and protein in the pharyngeal tonsils correlated with age,which gradually increased from newborn to adult and peaked in adulthood but declined in the old yak.Conclusion1.For the first time we clearly identified that there were five kinds of tonsils in yak,including the palatine tonsil,the tonsil of the soft palate,the lingual tonsil,the pharyngeal tonsil and the tubal tonsil.The palatine tonsil,the tonsil of the soft palate and the lingual tonsil were oropharynx tonsils covering stratified squamous epithelium.The pharyngeal tonsil and the tubal tonsil were nasopharynx tonsils covering pseudostratified ciliated columnar epithelium.There were well-developed primary and secondary lymphoid follicles in each tonsil.The results indicated that the tonsils formed an important immune defense ring at the junction of the digestive and respiratory tracts.2.The expression trends of IgA,IgG,SIRP? and CD68 positively correlated with the changes in the number of lymphoid follicles and crypts in adult yak tonsils.The results indicated that the palatine and pharyngeal tonsils were the most representative tonsils of yaks.They played an important role in the establishment of the immune response and the implementation of immune capacity.3.The palatine tonsils of newborn yak had no lymphoid follicles,while the pharyngeal tonsils had the primary lymphoid follicles.In both juvenile and adult yak palatine and pharyngeal tonsils,the primary and secondary lymphoid follicles were observed.The pharyngeal tonsils of old yak had the degenerate lymphoid follicles.The results indicated that the pharyngeal tonsil developed earlier than the palatine tonsils.The unique structures of the pharyngeal tonsil were more suitable for the absorption of antigens and the initiation of immune responses.4.The expression trends of IgA,IgG,SIRP? and CD68 in palatine and pharyngeal tonsils correlated with age and were also positively correlated with the trends in their size and the number of lymphoid follicles.The results also indicated that the dynamic expression of IgA,IgG,SIRP? and CD68 in the palatine and pharyngeal tonsils was closely related to their development.