Nematode infection in Alymphoplasia (aly) mice: worm species-dependent differential effect of defects of the gut-associated lymphatic tissue system

Acceleration of Trichinella spiralis worm expulsion by leukotriene B4 receptor binding inhibition

AIMS

Helminth infection typically induces a Th2 inflammatory response that is characterized by eosinophilia, high levels of IgE and mast cells. LTB4 is generated from innate immune cells, such as neutrophils, macrophages and mast cells, in response to a range of stimuli. It mainly acts on myeloid leukocytes, inducing the activation of integrins, adhesion to endothelium walls, and chemotaxis.

METHODS AND RESULTS

The objective of the present study was to determine the role of the LTB4 receptor in Trichinella spiralis expulsion. We treated mice with the LTB4 receptor antagonist before infection with T. spiralis. We observed that the number of mast cells and worm infection decreased following treatment with the BLT antagonist during the intestinal phase. We also demonstrated that blocking the LTB4 receptor inhibited neutrophil and eosinophil infiltration.

CONCLUSIONS

Further studies are required to investigate the specific mechanism of mast cell number decrease and worm infection and the in vitro interactions between LTB4 and worm expulsion.

Detection of α-defensin in eosinophils in helminth-infected mouse model

α-defensin is a potent antimicrobial peptide secreted from intestinal mucosal epithelial cells, such as Paneth cells, and affects not only bacteria but also parasites and fungi. Recently, human eosinophils have also been shown to produce α-defensin, but no studies have been done on other animals. In this study, we attempted to detect α-defensin protein in mouse eosinophils infiltrating the intestinal mucosa during a helminth infection using Zamboni fixation and immunohistochemistry. Most of the eosinophils infiltrating the intestinal mucosa during helminth infection were positive for α-defensin. The expression level of α-defensin mRNA was 50 fold that in the control. Meanwhile, the number of Paneth cells was doubled, and their α-defensin fluorescence intensity was increased. These results suggested that eosinophils are also important producers of α-defensin, such as Paneth cells in mice, and that α-defensin produced from eosinophils might be involved in defensive mechanisms against helminths. Moreover, the experimental system used in this study is a good model to study the generation of α-defensin by eosinophils.

Enhanced protection against Heligmosomoides polygyrus in IL-2 receptor β-chain overexpressed transgenic mice with intestinal mastocytosis

IL-2 receptor β-chain overexpressed transgenic (Tg2Rβ) mice lack NK cells, but the development of other lymphocyte subsets and macrophages remained apparently intact. These mice also exhibit intestinal mastocytosis. Helminth infection induces various immune responses, such as mast cells, goblet cells, eosinophils and IgE, mediated by Th2 cytokines. IL-4 is also important in the regulation of resistance and susceptibility to Heligmosomoides polygyrus infection. However, there are contradictory results about the relation between resistance to H. polygyrus and intestinal mastocytosis. The present study showed that Tg2Rβ mice suppressed worm fecundity with mastocytosis without an increase of the levels of goblet cells, eosinophils and IgE compared with control mice. These results clearly indicated that mast cells have the ability for to protect against H. polygyrus infection. However, additional studies are required to evaluate protective effector mechanisms against H. polygyrus.

Intestinal smooth muscle cells locally enhance stem cell factor (SCF) production against gastrointestinal nematode infections

Smooth muscle cells can produce stem cell factor (SCF) in the normal state for the preservation of mast cells, but it is still unknown whether smooth muscle cells can enhance SCF production in response to the pathological stimuli. The present study showed that smooth muscle cells in mast cell-increased regions around worm cysts of intestinal nematodes significantly enhanced SCF gene expression compared with mast cell non-increased regions in same sample. SCF gene expression in mast cell non-increased regions in nematode-infected mice showed almost the same level as in non-infected control groups. These results indicate that smooth muscle cells can locally enhance SCF gene expression, and may have a role in local immunological reactions as growth factor-producing cells.