The structure and distribution of the mucosa-associated lymphoid tissue (MALT) throughout the large intestine of 10 Bactrian camels were comparatively studied by anatomical and histological methods. The results showed that Peyer's patches (PPs) were mainly located on the mucosal surfaces of the entire ileocecal orifice, the beginning of the cecum and the first third of the colon. The shape of PPs gradually changed from "scrotiform" to "faviform" along the large intestine with the scrotiform PP as the major type in the ileocecal orifice. The distribution density also gradually decreased from the ileocecal orifice to the colon. The histological observations further revealed that the MALT in the form of PPs or isolated lymphoid follicles (ILF) and lamina propria lymphocytes was mainly present in the lamina propria and submucosa from the entire ileocecal orifice, where the muscularis mucosa is usually incomplete, to the colonic forepart. In addition, lymphoid tissue was much more abundant in the lamina propria and submucosa of the ileocecal orifice as compared to the cecum and colon. Statistically, the MALT of the ileocecal orifice contained a higher number of lymphoid follicles (37.7/10 mm 2 ) than that of the cecum, colon, or rectum (P < 0.05). The germinal centers of the lymphoid follicles were clearly visible. Together, our data suggest that the ileocecal orifice constitutes the main inductive site for the mucosal immunity in the large intestine of the Bactrian camel; and that scrotiform PPs are likely to the result of long-term adaptation of the Bactrian camel to the harsh living environment.

Post-weaning diarrhea commonly occurs in piglets and results in significant economic loss to swine producers. non-antibiotic measures for managing post-weaning diarrhea are critically needed. Duannai-An, a probiotic produced from the yeast fermentation of egg whites, was previously shown to optimize intestinal flora and reduce the incidence of clinical diarrhea in weaning piglets. To study the effects of Duan-Nai-An on mucosal integrity and immunity in pig intestine, we examined the microstructure and ultrastructure of the intestines of weaned pigs with or without Duan-nai-An as a feed supplement. the piglets of the Duan-nai-An-fed group developed intestines with intact columnar epithelia covered by tightly packed microvilli on the apical surface. However, piglets of the control group (no supplement) showed villous atrophy and thinning, microvillus slough, and in the severe cases, damage of intestinal epithelia and exposure of the underlying lamina propria. Moreover, piglets of the Duan-nai-An-fed group showed apparent plasmocyte hyperplasia, increased lymphoid nodule numbers, well-developed peyer's patchs, and apparent germinal centers. the lymphoid tissues of the control group were far less developed, showing lymph node atrophy, lymphocyte reduction, degeneration, and necrosis. these results indicate that Duan-nai-An improves the development of the intestinal structures and lymphoid tissues and promotes intestinal health in weaned piglets. The gastrointestinal (GI) tract is the largest immune organ in the body 1,2. The epithelial lining of the GI tract is the surface that is in close contact with the external environment. The GI tract also provides the microenvironment for the development and differentiation of the intestinal immune cells. The intestinal epithelial cells play important roles not only in food digestion and nutrient absorption, but also in immune defense and immune tolerance 3. More than 50% of the body's lymphoid tissue is distributed in the intestinal mucosa, bearing an important immune function and constituting the body's first barrier against pathogenic microorganism invasions 4. A diverse and large number of microorganisms are found in the GI tract. Gut microbiota play very important roles in the growth, anti-infection, immune regulation, metabolism and intestinal health of the host 5-8 , and most studies mainly focused on evaluating the impact of bacterial flora on animal nutrition 9-11. Recently, more and more work has been devoted to understanding the microbiota-intestinal mucosa interaction, how the interaction form a mechanical, immunological, and biological barrier against pathogen invasion and endotoxin translocation, and how gut microbiota modulates the development and function of the mucosal immune system 5,12-15. Weaning is one of the most stressful events in the swine production process and disturbs the intestinal flora of piglets, often compromising the intestinal structure and mucosal barrier 16. Because of the disruption, weaning piglets may have decreased intestinal mucosal im...

The distribution, size, and appearance of Peyer's patches vary according to species. In order to determine the anatomical characteristics of Peyer's patches in small intestine of Bactrian camel, and age-related changes in the number of Peyer's patches, 40 Bactrian camels of the following four age groups were studied: young (0.5-2 years), pubertal (3-5 years), middle-aged (6-16 years), and old (17-20 years). The exact number of Peyer's patches was recorded, and the appearance of Peyer's patches was described in detail. The results indicated that Peyer's patches of Bactrian camels not only have a particular anatomical location and distinct appearance but also change with age. They were distributed in the whole small intestine and there were four distinct types of Peyer's patches: nodular, faviform, cup-shaped, and cystic form Peyer's patches. However, the nodular and cystic form Peyer's patches are specific to Bactrian camel, which have not been found in other animals including Dromedary camel. In addition, the distribution density of Peyer's patches in ileum was the maximum, then was jejunum and duodenum. Further statistical analysis showed that the number of Peyer's patches was altered with age. The number peaked in 5-year-old camels and declined subsequently with age. However, there was little change in the size of Peyer's patches in different age groups; no age-related macroscopic variations in the shape or size of the Peyer's patches were found. Results obtained from this study provide the basic information to further study on the gastrointestinal mucosal immunity of Bactrian camel.