Intravenous lipopolysaccharide challenge alters ruminal bacterial microbiota and disrupts ruminal metabolism in dairy cattle.

In the present study, three primiparous lactating Holstein cows (260-285 d in lactation) were used in a 3 × 3 Latin square design to assess the effects of three doses (0.0, 0.4 and 0.8 µg/kg body weight) of lipopolysaccharide (LPS, Escherichia coli 0111:B4) on changes in ruminal microbiota and ruminal fermentation. Ruminal pH was linearly decreased (P< 0.001) by LPS challenge, and the concentrations of acetate, propionate, butyrate, total volatile fatty acids and amino N increased linearly (P< 0.001) according to the LPS dose. LPS infusion linearly decreased (P< 0.001) the organic matter degradability of alfalfa hay and soyabean meal in the rumen, but did not affect (P>0.10) the gene expression of Na⁺/K⁺-ATPase and monocarboxylic acid transporter-1, -2 and -4. A plot of principal coordinate analysis based on unweighted UniFrac values and analysis of molecular variance revealed that the structure of ruminal bacterial communities in the control was distinct from that of the ruminal microbiota in the cattle exposed to LPS. At the phylum level, when compared with the control group, LPS infusion in the tested cows linearly increased (P< 0.05) the abundance of Firmicutes, and linearly decreased (P< 0.05) the percentage of Bacteroidetes, Tenericutes, Spirochaetes, Chlorobi and Lentisphaerae. To our knowledge, this is the first study to report that intravenously LPS challenge altered the ruminal bacterial microbiota and fermentation profiles. The present data suggest that systemic LPS could alter ruminal environment and ruminal microbiota composition, leading to a general decrease in fermentative activity.

T cell subsets and Langerhans cells in the forestomach mucosa of adult sheep and sheep foetuses.

As part of a study on leukocytes in the ruminant forestomach the occurrence and distribution of T cells and major histocompatibility complex Class II positive (MHC-II+) cells in the forestomach mucosa of sheep were investigated. Samples were taken from the reticulum, atrium ruminis, ventral rumen, dorsal rumen and omasum of five healthy adult ewes and seven nearly fullborne foetuses. Frozen sections were stained with an indirect immunoperoxidase method using monoclonal antibodies against sheep MHC-II, CD4 and CD8 molecules and the sheep gamma delta T cell receptor. Both MHC-II+ cells and T cells were distributed along the basal lamina of the epithelium, with either mainly intraepithelial (CD8+ and gamma delta +cells) or mainly subepithelial (MHC-II+ and CD4+ cells) location. The MHC-II+ cells showed dendritic morphology and were interpreted as Langerhans cells. In adults ewes CD4+T cells comprised the major T cell subset at all sample sites. The number of T cells declined from the atrium ruminis through the ventral rumen to the dorsal rumen, while the number of Langerhans cells showed no marked variation between different sample sites. In foetuses, Langerhans cells showed a relatively high prevalence, while T cells were sparse and showed a more random distribution in the rumen wall. No marked variation between sample sites were observed in the fetal forestomachs. It is concluded that Langerhans cells and T cells are normally present in the forestomach mucosa of sheep, and it is suggested that the Langerhans cells represent a constituent component, while the prevalence and distribution of T cells may be influenced by antigen leakage through the epithelium.

Langerhans cells in the epithelium of the bovine forestomach: their role in the primary immune response.

Dendritic, migratory, lymphoid cells identical to the Langerhans cells of the epidermis, have been found in the epithelium of the bovine forestomach. They also possess the characteristic Langerhans cell granules. It can be assumed that these epithelial lymphocytes, (or Langerhans cells) as has been reported for the epidermal Langerhans cells, are antigen detectors and therefore form the first line of defence in the general immunological response of the body. The author suggests that the Langerhans cells of the forestomach be named epithelial lymphocytes. The existence of Langerhans cell granules has not yet been reported in the epithelial lymphocytes of the true stomach, intestines and respiratory epithelium.