title: Dose-dependent effects of Lactobacillus rhamnosus on serum interleukin-17 production and intestinal T-cell responses in pigs challenged with Escherichia coli.
abstract: The mechanism underlying the dose effect of probiotics on ameliorating diarrhea has not been fully elucidated. Here, low (1 × 10(9) CFU/ml) or high (1 × 10(11) CFU/ml) doses of Lactobacillus rhamnosus ATCC 7469 were administered orally to piglets for 1 week before F4 (K88)-positive enterotoxigenic Escherichia coli (F4(+) ETEC) challenge. Administration of a low, but not a high, dose of L. rhamnosus decreased the percentage of CD3(+) CD4(+) CD8(-) T cells in the peripheral blood. Notably, transiently increased serum concentrations of interleukin-17A (IL-17A) were observed after F4(+) ETEC challenge in pigs pretreated with a high dose of L. rhamnosus. Administration of L. rhamnosus increased the percentage of the small intestinal lamina propria CD3(+) CD4(+) CD8(-) cells and Peyer's patch CD3(+) CD4(-) CD8(-) and CD3(-) CD4(-) CD8(+) cells. The percentage of ileal intraepithelial CD3(+) CD4(-) CD8(+) cells increased only in the high-dose piglets. Administration of L. rhamnosus downregulated expression of ileal IL-17A after F4(+) ETEC challenge but had no effect on expression of gamma interferon (IFN-γ), IL-12, IL-4, and FOXP3 mRNA in the small intestine. Expression of jejunal IL-2, ileal transforming growth factor β1 (TGF-β1), and ileal IL-10 was upregulated in the low-dose piglets after F4(+) ETEC challenge. Our findings suggest that amelioration of infectious diarrhea in piglets by L. rhamnosus is associated with the generation of lamina propria CD3(+) CD4(+) CD8(-) T cells, the expansion of Peyer's patch CD3(+) CD4(-) CD8(-) and CD3(-) CD4(-) CD8(+) cells, and the attenuation of F4(+) ETEC-induced increase in CD3(+) CD4(+) CD8(+) T cells in the small intestine. However, consumption of high doses of L. rhamnosus may increase levels of serum IL-17A after F4(+) ETEC challenge, thus eliciting a strong proinflammatory response.
authors.affiliation: College of Veterinary Medicine, China Agricultural University, Beijing, China.
authors.forename: Yao-Hong
authors.initials: YH
authors.lastname: Zhu
authors.forename: Xiao-Qiong
authors.initials: XQ
authors.lastname: Li
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Dong
authors.initials: D
authors.lastname: Zhou
authors.forename: Hao-Yu
authors.initials: HY
authors.lastname: Liu
authors.forename: Jiu-Feng
authors.initials: JF
authors.lastname: Wang
mesh_terms: D000818:Animals; D001769:Blood / Q000276:immunology; D054307:Enterotoxigenic Escherichia coli / Q000276:immunology*; D007155:Immunologic Factors / Q000008:administration & dosage*; D020381:Interleukin-17 / Q000097:blood*; D007413:Intestinal Mucosa / Q000276:immunology*; D052201:Lacticaseibacillus rhamnosus / Q000276:immunology*; D019936:Probiotics / Q000008:administration & dosage*; D013552:Swine; D016176:T-Lymphocyte Subsets / Q000276:immunology*
chemical_list: D007155:Immunologic Factors; D020381:Interleukin-17