Poster Presentation Australasian Society for Immunology Annual Scientific Meeting 2014

Susceptibility to ileitis of SKG mice under germ free conditions and after colonization with a limited bacterial consortium negatively correlates with the proportion of colonic Foxp3+ regulatory Tcells (#333)

Zaied Bhuyan 1 , Olga Zbarskaya 1 , Alicia Kang 1 , Linda Rehaume 1 , Mark Morrison 1 , Ranjeny Thomas
  1. UQDI (TRI), Woolloongabba, QLD, Australia

Background

Microbial b-glucan (curdlan)-treated BALB/c ZAP-70W163C (SKG) mutant mice develop IL-23-dependent spondyloarthritis with ileitis when housed under specific pathogen-free (SPF) but not germ-free (GF) conditions. Curdlan-treated GF SKG mice recolonized with Charles RiverAltered Schaedler flora (ASF), a limited bacterial consortium, are also susceptible to spondyloarthritis and ileitis. Curdlan-treated BALB/c mice are resistant to ileitis and cohousing with BALB/c mice reduces the susceptibility of SKG mice to ileitis. This study was undertaken to investigate dysbiosis in SKG mice recolonised with ASF and its relationship to mucosal regulation in the host.

Methods

GF SKG mice were colonised with ASF for three weeks, and then injected intraperitoneally with curdlan alone or curdlan and anti-IL-23 antibody for eight weeks. Bacterial 16S-rDNA was extracted from faecal pellets and the copy numbers of individual ASF species were determined using qPCR. Lamina propria (LP) cells were collected from colon and the proportion of Foxp3+CD4+ regulatory T cells (Tregs) determined by FACS.

Results

Four out of eight ASF bacterial strains (Bacteroides sp., Clostridium sp., Lactobacillus murinus, Flexostipes gr.) were identified in the faeces of ASF-colonised SKG mice. Dysbiosis occurred in curdlan-treated SKG mice: the load of the anaerobic gram negative Bacteroides sp. increased in female mice after curdlan in an IL-23 dependent manner. In the colonic LP of GF male SKG mice, 10% of CD4+ T cells were Foxp3+, while 7% Tregs were reported in BALB/c GF mice. After colonization with ASF, Tregs were reduced to 5 % in SKG mice, but were reported to increase to 15 % in BALB/c mice recolonized with ASF. Depletion of Tregs from curdlan-treated female SKG mice under SPF-conditions resulted in rapid and severe disease development.

Conclusions

These preliminary data suggest that the frequency of colonic Treg negatively correlates with susceptibility to ileitis in SKG mice. Furthermore after colonisation with ASF, dysbiosis in SKG mice is associated with unusual reduction in colonic Treg, which appears to relate to host genotype.