RESUMO
Eosinophils are present in the thymus of mammals, yet their function at this site during homeostatic development is unknown. We used flow cytometry to determine the abundance and phenotype of eosinophils (here defined as SSchigh SiglecF+ CD11b+ CD45+ cells) in the thymus of mice during the neonatal period, the later postnatal period, and into adulthood. We show that both the total number of thymic eosinophils and their frequency among leukocytes increase over the first 2 wk of life and that their accumulation in the thymus is dependent on the presence of an intact bacterial microbiota. We report that thymic eosinophils express the interleukin-5 receptor (CD125), CD80, and IDO, and that subsets of thymic eosinophils express CD11c and major histocompatibility complex II (MHCII). We found that the frequency of MHCII-expressing thymic eosinophils increases over the first 2 wk of life, and that during this early-life period the highest frequency of MHCII-expressing thymic eosinophils is located in the inner medullary region. These data suggest a temporal and microbiota-dependent regulation of eosinophil abundance and functional capabilities in the thymus.
Assuntos
Eosinófilos , Timo , Camundongos , Animais , Citometria de Fluxo , Complexo Principal de Histocompatibilidade , MamíferosRESUMO
Heligmosomoides polygyrus is a helminth which naturally infects mice and is widely used as a laboratory model of chronic small intestinal helminth infection. While it is known that infection with H. polygyrus alters the composition of the host's bacterial microbiota, the functional implications of this alteration are unclear. We investigated the impact of H. polygyrus infection on short-chain fatty acid (SCFA) levels in the mouse intestine and sera. We found that helminth infection resulted in significantly upregulated levels of the branched SCFA isovaleric acid, exclusively in the proximal small intestine, which is the site of H. polygyrus colonization. We next set out to test the hypothesis that elevating local levels of isovaleric acid was a strategy used by H. polygyrus to promote its own fitness within the mammalian host. To test this, we supplemented the drinking water of mice with isovalerate during H. polygyrus infection and examined whether this affected helminth fecundity or chronicity. We did not find that isovaleric acid supplementation affected helminth chronicity; however, we found that it did promote helminth fecundity, as measured by helminth egg output in the feces of mice. Through antibiotic treatment of helminth-infected mice, we found that the bacterial microbiota was required in order to support elevated levels of isovaleric acid in the proximal small intestine during helminth infection. Overall, our data reveal that during H. polygyrus infection there is a microbiota-dependent localized increase in the production of isovaleric acid in the proximal small intestine and that this supports helminth fecundity in the murine host.
Assuntos
Ácidos Graxos Voláteis/metabolismo , Interações Hospedeiro-Parasita , Mucosa Intestinal/metabolismo , Mucosa Intestinal/parasitologia , Nematospiroides dubius/fisiologia , Infecções por Strongylida/metabolismo , Infecções por Strongylida/parasitologia , Animais , Modelos Animais de Doenças , Metabolismo dos Lipídeos , CamundongosRESUMO
Intestinal helminth infection can impair host resistance to co-infection with enteric bacterial pathogens. However, it is not known whether helminth drug-clearance can restore host resistance to bacterial infection. Using a mouse helminth-Salmonella co-infection system, we show that anthelmintic treatment prior to Salmonella challenge is sufficient to restore host resistance to Salmonella. The presence of the small intestine-dwelling helminth Heligmosomoides polygyrus at the point of Salmonella infection supports the initial establishment of Salmonella in the small intestinal lumen. Interestingly, if helminth drug-clearance is delayed until Salmonella has already established in the small intestinal lumen, anthelmintic treatment does not result in complete clearance of Salmonella. This suggests that while the presence of helminths supports initial Salmonella colonization, helminths are dispensable for Salmonella persistence in the host small intestine. These data contribute to the mechanistic understanding of how an ongoing or prior helminth infection can affect pathogenic bacterial colonization and persistence in the mammalian intestine.
Assuntos
Coinfecção/microbiologia , Coinfecção/parasitologia , Resistência à Doença/fisiologia , Helmintíase/complicações , Enteropatias Parasitárias/complicações , Nematospiroides dubius/fisiologia , Salmonella/fisiologia , Animais , Modelos Animais de Doenças , Feminino , Microbioma Gastrointestinal , Intestinos/microbiologia , Intestinos/parasitologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Infecções por Salmonella/complicações , Salmonella typhiRESUMO
Conflicting data has emerged regarding a role for eosinophils in IgA production, with some reports that eosinophils support both secretory and circulating IgA levels during homeostasis. Previous studies have compared antibody levels between wildtype and eosinophil-deficient mice, but these mice were obtained from different commercial vendors and/or were not littermates. Thus, the possibility remains that extrinsic environmental factors, rather than an intrinsic lack of eosinophils, are responsible for the reports of reduced IgA in eosinophil-deficient mice. Here we used wild-type and eosinophil-deficient (ΔdblGATA) mice that were purchased from a single vendor, subsequently bred in-house and either co-housed as adults, co-reared from birth or raised as littermates. We found no differences in the levels of secretory IgA or in the numbers of small intestinal IgA-producing plasma cells between wild-type and ΔdblGATA mice, demonstrating that under controlled steady-state conditions eosinophils are not essential for the maintenance of secretory IgA in the intestinal tract. While we found that levels of IgM and IgE were significantly elevated in the serum of ΔdblGATA mice compared to co-reared or co-housed wild-type mice, no significant differences in these or other circulating antibody isotypes were identified between genotypes in littermate-controlled experiments. Our results demonstrate that eosinophils are not required to maintain secretory or circulating IgA production and the absence of eosinophils does not impact circulating IgG1, IgG2b, IgM, or IgE levels during homeostasis. These findings emphasize the importance of optimally controlling rearing and housing conditions throughout life between mice of different genotypes.