Rajka Borojevic

Intestinal microbiota influence the early postnatal development of the enteric nervous system

Normal gastrointestinal function depends on an intact and coordinated enteric nervous system (ENS). While the ENS is formed during fetal life, plasticity persists in the postnatal period during which the gastrointestinal tract is colonized by bacteria. We tested the hypothesis that colonization of the bowel by intestinal microbiota influences the postnatal development of the ENS.

Expression of Dual TCR on DO11.10 T Cells Allows for Ovalbumin-Induced Oral Tolerance to Prevent T Cell-Mediated Colitis Directed against Unrelated Enteric Bacterial Antigens

The triggering Ag for inflammatory bowel disease and animal models of colitis is not known, but may include gut flora. Feeding OVA to DO11.10 mice with OVA-specific transgenic (Tg) TCR generates Ag-specific immunoregulatory CD4+ T cells (Treg) cells. We examined the ability of oral Ag-induced Treg cells to suppress T cell-mediated colitis in mice. SCID-bg mice given DO11.10 CD4+CD45RBhigh T cells developed colitis, and cotransferring DO11.10 CD45RBlowCD4+ T cells prevented CD4+CD45RBhigh T cell-induced colitis in the absence of OVA. The induction and prevention of disease by DO11.10 CD4+ T cell subsets were associated with an increase in endogenous TCRα chain expression on Tg T cells. Feeding OVA to SCID-bg mice reconstituted with DO11.10 CD4+CD45RBhigh attenuated the colitis in association with increased TGF-β and IL-10 secretion, and decreased proliferative responses to both OVA and cecal bacteria Ag. OVA feeding also attenuated colitis in SCID-bg mice reconstituted with a mix of BALB/c and DO11.10 CD45RBhigh T cells, suggesting that OVA-induced Treg cells suppressed BALB/c effector cells. The expression of endogenous non-Tg TCR allowed for DO11.10-derived T cells to respond to enteric flora Ag. Furthermore, feeding OVA-induced Treg cells prevented colitis by inducing tolerance in both OVA-reactive and non-OVA-reactive T cells and by inducing Ag-nonspecific Treg cells. Such a mechanism might allow for Ag-nonspecific modulation of intestinal inflammation in inflammatory bowel disease.

Regulatory T Cells Modulate Staphylococcal Enterotoxin B-Induced Effector T-Cell Activation and Acceleration of Colitis

ABSTRACT Oral administration of bacterial superantigen Staphylococcus aureus enterotoxin B (SEB) activates mucosal T cells but does not cause mucosal inflammation. We examined the effect of oral SEB on the development of mucosal inflammation in mice in the absence of regulatory T (Treg) cells. SCID mice were fed SEB 3 and 7 days after reconstitution with CD4+ CD45RBhigh or CD4+ CD45RBhigh plus CD4+ CD45RBlow T cells. Mice were sacrificed at different time points to examine changes in tissue damage and in T-cell phenotypes. Feeding SEB failed to produce any clinical effect on SCID mice reconstituted with CD4+ CD45RBhigh and CD4+ CD45RBlow T cells, but feeding SEB accelerated the development of colitis in SCID mice reconstituted with CD4+ CD45RBhigh T cells alone. The latter was associated with an increase in the number of CD4+ Vβ8+ T cells expressing CD69 and a significantly lower number of CD4+ CD25+ Foxp3+ T cells. These changes were not observed in SCID mice reconstituted with both CD45RBhigh and CD45RBlow T cells. In addition, SEB impaired the development of Treg cells in the SCID mice reconstituted with CD4+ CD45RBhigh T cells alone but had no direct effect on Treg cells. In the absence of Treg cells, feeding SEB induced activation of mucosal T cells and accelerated the development of colitis. This suggests that Treg cells prevent SEB-induced mucosal inflammation through modulation of SEB-induced T-cell activation.

Slit/Robo-mediated chemorepulsion of vagal sensory axons in the fetal gut.

Background: The vagus nerve descends from the brain to the gut during fetal life to reach specific targets in the bowel wall. Vagal sensory axons have been shown to respond to the axon guidance molecule netrin and to its receptor, deleted in colorectal cancer (DCC). As there are regions of the gut wall into which vagal axons do and do not extend, it is likely that a combination of attractive and repellent cues are involved in how vagal axons reach specific targets. We tested the hypothesis that Slit/Robo chemorepulsion can contribute to the restriction of vagal sensory axons to specific targets in the gut wall. Results: Transcripts encoding Robo1 and Robo2 were expressed in the nodose ganglia throughout development and mRNA encoding the Robo ligands Slit1, Slit2, and Slit3 were all found in the fetal and adult bowel. Slit2 protein was located in the outer gut mesenchyme in regions that partially overlap with the secretion of netrin‐1. Neurites extending from explanted nodose ganglia were repelled by Slit2. Conclusions: These observations suggest that vagal sensory axons are responsive to Slit proteins and are thus repelled by Slits secreted in the gut wall and prevented from reaching inappropriate targets. Developmental Dynamics 242:9–15, 2013.

Combined absence of perforin and FasL in perf -/- x gld mice significantly decreases anti-CD3 induced enteropathy

COMBINED ABSENCE OF PERFORIN AND FASL IN PERF -/X cui MICE SIGNIFICANTLY DECREASES ANTI-CD3 INDUCED ENTEROPATHY. Michael Merger, Michelle A. Zysrnan, Rajka Borojevic, Eckhard R. Podack, Kenneth Croitoru, Dept of Internal Medicine I, Univ of Regensburg, Regensburg, Germany; Intestinal Disease Research Program, McMaster Univ, Hamilton, Canada; Dept of Micro and Immunol , Univ of Miami, Miami, FL.