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.

BackgroundTo explore the morphological evidence of immunoglobulin G (IgG) participating in intestinal mucosal immunity, 8 healthy adult Bactrian camels used. First, IgG was successfully isolated from their serum and rabbit antibody against Bactrian camels IgG was prepared. The IgG antibody secretory cells (ASCs) in small intestine were particularly observed through immumohistochemical staining, then after were analyzed by statistical methods.ResultsThe results showed that the IgG ASCs were scattered in the lamina propria (LP) and some of them aggregated around of the intestinal glands. The IgG ASCs density was the highest from middle segment of duodenum to middle segment of jejunum, and then in ended segment of jejunum and initial segment of ileum, the lowest was in initial segment of duodenum, in middle and ended segment of ileum.ConclusionsIt was demonstrated that the IgG ASCs mainly scattered in the effector sites of the mucosal immunity, though the density of IgG ASCs was different in different segment of small intestine. Moreover, this scatted distribution characteristic would provide a morphology basis for research whether IgG form a full-protection and immune surveillance in mucosal immunity homeostasis of integral intestine.

Secretory immunoglobulin A (SIgA) and immunoglobulin G (IgG) antibody-secreting cells (ASCs) are two important cell types in the mucosal immune system. This study aimed to explore the distribution of these ASC populations in the small intestine of Bactrian camels of different ages. Twenty-four Alashan Bactrian camels were divided into the following four age groups: young (1–2 years), pubertal (3–5 years), middle-aged (6–16 years) and old (17–20 years). SIgA and IgG ASCs in the intestinal mucosa lamina propria (LP) were observed and analyzed using immunohistochemcal techniques. The results from all age groups show that both SIgA and IgG ASCs were diffusely distributed in the intestinal LP, and some cells aggregated around the crypts. Moreover, the densities of the two ASC populations gradually increased from the duodenum to the jejunum and then decreased in the ileum. Meanwhile, there were more SIgA ASCs than IgG ASCs in the duodenum, jejunum, and ileum, and these differences were significant in the young and pubertal groups (P<0.05). In addition, the SIgA and IgG ASC densities increased from the young to the pubertal period, peaked at puberty, and then gradually decreased with age. The results demonstrate that the SIgA and IgG ASC distributions help to form two immunoglobulin barriers in the intestinal mucosa to provide full protection, helping to maintain homeostasis. These findings also underscore the importance of researching the development and degeneration of intestinal mucosal immunity in Bactrian camels.

BackgroundThe neonatal Fc receptor (FcRn) plays a crucial role in transporting IgG and associated antigens across polarized epithelial barriers in mucosal immunity. However, it was not clear that FcRn expression in aggregated lymphoid nodules area (ALNA) in abomasum, a unique and important mucosal immune structure discovered only in Bactrian camels. In the present study, 27 Alashan Bactrian camels were divided into the following five age groups: fetus (10–13 months of gestation), young (1–2 years), pubertal (3–5 years), middle-aged (6–16 years) and old (17–20 years). The FcRn expressions were observed and analyzed in detail with histology, immunohistochemistry, micro-image analysis and statistical methods.ResultsThe results showed that the FcRn was expressed in mucosal epithelial cells of ALNA from the fetus to the old group, although the expression level rapidly declined in old group; moreover, after the ALNA maturated, the FcRn expression level in the non-follicle-associated epithelium (non-FAE) was significantly higher than that in FAE (P < 0.05). In addition, the FcRn was also expressed in the vessel endothelium, smooth muscle tissue, and macrophages and dendritic cells (DCs) of secondary lymphoid follicles (sLFs).ConclusionsIt was demonstrated that FcRn was mainly expressed in non-FAE, the effector sites, although which was expressed in FAE, the inductive sites for mucosal immunity. And it was also expressed in DCs and macrophages in sLFs of all ages of Bactrian camels. The results provided a powerful evidence that IgG (including HCAb) could participate in mucosal immune response and tolerance in ALNA of Bactrian camels through FcRn transmembrane transport.

The female reproductive tract develops from its embryonic precursor, the Müllerian duct. In close proximity to the Müllerian duct lies the precursor for the male reproductive tract, the Wolffian duct, which is eliminated in the female embryo during sexual differentiation. We discovered that a component of the Wolffian duct, its mesenchyme, is not eliminated after sexual differentiation. Instead, the Wolffian duct mesenchyme underwent changes in transcriptome and chromatin accessibility from male tract to female tract identity, and became a unique mesenchymal population in the female reproductive tract with localization and transcriptome distinct from the mesenchyme derived from the Müllerian duct. Partial ablation of the Wolffian duct mesenchyme stunted the growth of the fetal female reproductive tract in ex vivo organ culture. These findings reveal a new fetal origin of mesenchymal tissues for female reproductive tract formation and reshape our understanding of sexual differentiation of reproductive tracts.