Germ-free mice produce high levels of interferon-gamma in response to infection with Leishmania major but fail to heal lesions

Abstract

In order to investigate the importance of the host microbiota on differentiation of T cell subsets in response to infection, Swiss/NIH germ-free mice and conventional (microbiota-bearing) mice were infected with Leishmania major, and lesion development, parasite loads, and cytokine production were assessed. Germ-free mice failed to heal lesions and presented a higher number of parasites at the site of infection than their conventional counterparts. In addition, histopathological analysis indicated a higher density of parasitized macrophages in lesions from germ-free mice than in conventional mice. The initial production of interleukin (IL)-12 and interferon-gamma (IFN-gamma) in germ-free mice was comparable to the conventional controls. Also, germ-free mice produced elevated levels of IFN-gamma and lower levels of IL-4 throughout the course of infection, suggesting the development of a Th1 response. Macrophages from germ-free mice exposed to IFN-gamma and infected with amastigotes in vitro were not as efficient at killing parasites as macrophages from conventional animals. These observations indicate that the microbiota is not essential for the development of Th1 immune responses, but seems to be important for macrophage activation.

Transient TLR Activation Restores Inflammatory Response and Ability To Control Pulmonary Bacterial Infection in Germfree Mice

“…Our results showed that germfree mice died much earlier after bacterial infection, whereas conventional animals, which are capable of inflaming in response to the bacterial challenge, survived for .3 d. Our results are in agreement with others, which demonstrated the increase of susceptibility to parasite infection in absence of commensal microbiota. For example, germ-free mice have decreased capacity to deal with Leishmania major (24) and Trypanosoma cruzi infections (25). Altogether, these experiments in germfree mice would suggest that the ability to inflame in response to bacteria, and possibly other parasites, is evolutionarily relevant.…”

Low and high-dose intradermal infection with Leishmania majorand Leishmania amazonensis in C57BL/6 mice

“…Cultures of spleen cells and lymph nodes were performed as previously described (Oliveira et al 2005). Cells were cultured in medium alone or with 50 µg/mL of a homolog antigen for 24 h for TNF assays or for 72 h for IFN-γ and IL-10 assays.…”

“…Cells were cultured in medium alone or with 50 µg/mL of a homolog antigen for 24 h for TNF assays or for 72 h for IFN-γ and IL-10 assays. IFN-γ was assayed using the monoclonal antibody R46A2, a polyclonal rabbit anti-mouse IFN-γ prepared in our laboratory and an anti-rabbit IgG conjugated with peroxidase (Zymed Laboratories, Inc, San Francisco, CA, USA) (Oliveira et al 2005). ABTS (Sigma-Aldrich, Inc, St. Louis, MO, USA) and hydrogen peroxide were used as substrates for peroxidase.…”

Gut microbiome and anticancer immune response: really hot Sh*t!

“…First, colonization by commensal microorganisms is key to immune development. [9][10][11][12] Second, the commensal community keeps in check invading pathogens and prevents them from expressing virulence. 13,14 Third, the intestinal microbiota appears to digest glycans and regulate fat storage in mice and potentially in humans.…”