Sarah Brewer

Commensal Microbiota and CD8+ T Cells Shape the Formation of Invariant NKT Cells

Commensal bacteria play an important role in formation of the immune system, but the mechanisms involved are incompletely understood. In this study, we analyze CD1d-restricted invariant NKT (iNKT) cells in germfree mice and in two colonies of C57BL/6 mice termed conventional flora and restricted flora (RF), stably bearing commensal microbial communities of diverse but distinct composition. In germfree mice, iNKT cells were moderately reduced, suggesting that commensal microbiota were partially required for the antigenic drive in maintaining systemic iNKT cells. Surprisingly, even greater depletion of iNKT cell population occurred in RF mice. This was in part attributable to reduced RF levels of intestinal microbial taxa (Sphingomonas spp.) known to express antigenic glycosphingolipid products. However, memory and activated CD8+ T cells were also expanded in RF mice, prompting us to test whether CD8+ T cell activity might be further depleting iNKT cells. Indeed, iNKT cell numbers were restored in RF mice bearing the CD8α−/− genotype or in adult wild-type RF mice acutely depleted with anti-CD8 Ab. Moreover, iNKT cells were restored in RF mice bearing the Prf1−/− phenotype, a key component of cytolytic function. These findings indicate that commensal microbiota, through positive (antigenic drive) and negative (cytolytic depletion by CD8+ T cells) mechanisms, profoundly shape the iNKT cell compartment. Because individuals greatly vary in the composition of their microbial communities, enteric microbiota may play an important epigenetic role in the striking differences in iNKT cell abundance in humans and therefore in their potential contribution to host immune status.

Molecular imaging of murine intestinal inflammation with 2-deoxy-2-[18F]fluoro-D-glucose and positron emission tomography.

BACKGROUND & AIMS 2-Deoxy-2-[(18)F]fluoro-d-glucose (FDG) uptake by positron emission tomography (PET), a measure of glucose transporter activity, has been used to detect mucosal inflammation. However, there is limited understanding of the biologic basis of mucosal FDG uptake. METHODS A contrast-based computed tomographic isocontour method was developed to identify intestinal anatomic regions, and FDG uptake was integrated over these regions to achieve reproducible quantification during longitudinal assessment of individual mice. Intestinal FDG uptake was compared with histologic scores and with glucose transporter 1 levels in mucosal immune cells by flow cytometry. RESULTS Intestinal FDG uptake quantitatively correlated with disease activity in mild (C3H/HeJ.IL-10(-/-)) and severe (129.Galphai2(-/-), CD4(+) CD45RB(high), and Galphai2(-/-) CD3(+) transfer) murine colitis models at all time points examined (P < .05) and was sufficiently sensitive to detect preclinical inflammation. FDG uptake was correlated by flow cytometric detection of glucose transporter 1 levels in mucosal CD4(+) T lymphocyte but not other intestinal immune cell types. CD4(+) T-cell transfer in vivo confirmed that mucosal FDG uptake was associated with the activated but not quiescent state. When intestinal inflammation was increased by treatment with piroxicam and decreased with anti-TL1A treatment, FDG uptake was correspondingly altered. CONCLUSIONS This study clarifies the cellular basis of FDG signal in intestinal inflammation and introduces computed tomographic isocontour analysis of FDG-PET imaging for standardized quantitation of immune colitis.

Systemic Control of Plasmacytoid Dendritic Cells by CD8+ T Cells and Commensal Microbiota

The composition of the intestinal microbial community is a distinctive individual trait that may divergently influence host biology. Because dendritic cells (DC) regulate the quality of the host response to microbiota, we evaluated DC in mice bearing distinct enteric microbial communities divergent for colitis susceptibility. Surprisingly, a selective, systemic reduction of plasmacytoid dendritic cells (pDC) was observed in isogenic mice with different microbiota: restricted flora (RF) vs specific pathogen free (SPF). This reduction was not observed in germfree mice, suggesting that the pDC deficiency was not simply due to a lack of intestinal microbial products. The microbial action was linked to cytotoxic CD8+ T cells, since pDC in RF mice were preserved in the CD8−/− and perforin−/− genotypes, partially restored by anti-CD8β Ab, and augmented in SPF mice bearing the TAP−/− genotype. Direct evidence for pDC cytolysis was obtained by rapid and selective pDC depletion in SPF mice transferred with RF CD8+ T cells. These data indicate that commensal microbiota, via CTL activation, functionally shape systemic immune regulation that may modify risk of inflammatory disease.

Resident enteric microbiota and CD8+ T cells shape the abundance of marginal zone B cells

Since enteric microbial composition is a distinctive and stable individual trait, microbial heterogeneity may confer lifelong, non‐genetic differences between individuals. Here we report that C57BL/6 mice bearing restricted flora microbiota, a distinct but diverse resident enteric microbial community, are numerically and functionally deficient in marginal zone (MZ) B cells. Surprisingly, MZ B‐cell levels are minimally affected by germ‐free conditions or null mutations of various TLR signaling molecules. In contrast, MZ B‐cell depletion is exquisitely dependent on cytolytic CD8+ T cells, and includes targeting of a cross‐reactive microbial/endogenous MHC class 1B antigen. Thus, members of certain enteric microbial communities link with CD8+ T cells as a previously unappreciated mechanism that shapes innate immunity dependent on innate‐like B cells.

Villous B Cells of the Small Intestine Are Specialized for Invariant NK T Cell Dependence

B cells are important in mucosal microbial homeostasis through their well-known role in secretory IgA production and their emerging role in mucosal immunoregulation. Several specialized intraintestinal B cell compartments have been characterized, but the nature of conventional B cells in the lamina propria is poorly understood. In this study, we identify a B cell population predominantly composed of surface IgM+ IgD+ cells residing in villi of the small intestine and superficial lamina propria of the large intestine, but distinct from the intraepithelial compartment or organized intestinal lymphoid structures. Small intestinal (villous) B cells are diminished in genotypes that alter the strength of BCR signaling (Bruton tyrosine kinasexid, Gαi2−/−), and in mice lacking cognate BCR specificity. They are not dependent on enteric microbial sensing, because they are abundant in mice that are germfree or genetically deficient in TLR signaling. However, villous B cells are reduced in the absence of invariant NK T cells (Jα18−/− or CD1d−/− mice). These findings define a distinct population of conventional B cells in small intestinal villi, and suggest an immunologic link between CD1-restricted invariant NK T cells and this B cell population.

Integration of B cells and CD8 + T in the protective regulation of systemic epithelial inflammation

Mechanisms that control abnormal CD4(+) T cell-mediated tissue damage are a significant factor in averting and resolving chronic inflammatory epithelial diseases. B cells can promote such immunoregulation, and this is thought to involve interaction with MHC II- or CD1-restricted regulatory T cells. The purpose of this study is to genetically define the interacting cells targeted by protective B cells, and to elucidate their regulatory mechanisms in CD4(+) T cell inflammation. Transfer of G alpha i2-/- CD3(+) T cells into lymphopenic mice causes a dose-dependent multi-organ inflammatory disease including the skin, intestine, and lungs. Disease activity is associated with elevated levels of serum TNF-alpha and IFN-gamma, and an activated IL-17 producing CD4(+) T cell population. Mesenteric node B cells from wild type mice suppress disease activity, serum cytokine expression, and levels of CD4(+) T cells producing TNF-alpha IFN-gamma, and IL-17. The protective function of B cells requires genetic sufficiency of IL-10, MHC I and TAP1. Regulatory B cells induce the expansion and activation of CD8(+) T cells, which is correlated with disease protection. These results demonstrate that CD8(+) T cells can ameliorate lymphopenic systemic inflammatory disease, through peptide/MHC I-dependent B cell interaction.

Colitis immunoregulation by CD8+ T cell requires T cell cytotoxicity and B cell peptide antigen presentation

Deficient immunoregulation by CD4+ T cells is an important susceptibility trait for inflammatory bowel disease, but the role of other regulatory cell types is less understood. This study addresses the role and mechanistic interaction of B cells and CD8+ T cells in controlling immune-mediated colitis. The genetic requirements for B cells and CD8+ T cells to confer protective immunoregulation were assessed by cotransfer with colitogenic Galphai2-/- T cells into immune-deficient mice. Disease activity in Galphai2-/- T cell recipients was evaluated by CD4+ T intestinal lymphocyte abundance, cytokine production levels, and large intestine histology. B cells deficient in B7.1/B7.2, CD40, major histocompatibility complex (MHC) II (Abb), or native B cell antigen receptor (MD4) were competent for colitis protection. However, transporter-1-deficient B cells failed to protect, indicating a requirement for peptide MHC I presentation to CD8+ T cells. CD8+ T cells deficient in native T cell receptor repertoire (OT-1) or cytolysis (perforin-/-) also were nonprotective. These finding reveal an integrated role for antigen-specific perforin-dependent CD8+ T cell cytotoxicity in colitis immunoregulatory and its efficient induction by a subset of mesenteric B lymphocytes.

Abstract 5310: Positron emission tomography imaging of endometrial cancer using an anti-EMP2 minibody

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Endometrial cancer is increasingly affecting pre-menopausal women, prompting a need to develop fertility-sparing therapy, and monitor response to treatment by quantitative non-invasive strategies. Epithelial membrane protein 2 (EMP2) is a tetraspan protein associated with surface localization and function of cancer-relevant integrin isoforms, and EMP2 expression in endometrial cancer correlates with increasing cancer stage and poor prognosis. As EMP2 is highly expressed in endometrial cancer, this pre-clinical study tested the feasibility of non-invasive detection of human endometrial tumor xenografts using a radiolabeled anti-EMP2 diabody and positron emission tomography (PET). EMP2 biodistribution in murine organ was determined by western blot and immunohistochemistry. Anti-EMP2 minibody (MB83) fragment was designed and transfected into CHO-K1 cells. Purified minibody was DOTA conjugated and the binding activity was tested by flow cytometry using endometrial cancer cell line, Hec-1A/EMP2 cells. Then conjugated minibody was chelated with Cu-64. In vivo biodistribution of Cu-64 labeled MB83 in Balb/c nu/nu mice were determined by microPET imaging and AMIDE sofeware. MB83 location was determined by microPET in mice bearing Hec1a/EMP2 xenograft. EMP2 expression was detectable in the lung but not other organs by either western or immunohistochemistry. The absence of detectable EMP2 protein in the organs reflects that the target tumor with high EMP2 protein could uptake anti-EMP2 antibody which could be observed by microPET. The specific uptake of MB83 minibody within the Hec1a/EMP2 tumor can be seen both visually and quantitatively. Selective tumor uptake became more specific over time. In contrast, 2-deoxy-2-[18F]fluoro-D- glucose (FDG) microPET uptake by HEC-1A/EMP2 was minimal, reflecting the poor detection of gynecologic cancer cell types by conventional FDG-PET imaging. These findings demonstrate the feasibility of imaging endometrial and other gynecological cancers which have upregulated EMP2 expression using recombinant anti-EMP2 antibodies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5310. doi:10.1158/1538-7445.AM2011-5310

303 Systemic Control of Plasmacytoid Dendritic Cells By CD8+ T Cells and Commensal Microbiota

The composition of the intestinal microbial community is a distinctive individual trait that may divergently influence host biology. Because dendritic cells (DC) regulate the quality of the host response to microbiota, we evaluated DC in mice bearing distinct enteric microbial communities divergent for colitis susceptibility. Surprisingly, a selective, systemic reduction of plasmacytoid dendritic cells (pDC) was observed in isogenic mice with different microbiota: restricted flora (RF) vs specific pathogen free (SPF). This reduction was not observed in germfree mice, suggesting that the pDC deficiency was not simply due to a lack of intestinal microbial products. The microbial action was linked to cytotoxic CD8(+) T cells, since pDC in RF mice were preserved in the CD8(-/-) and perforin(-/-) genotypes, partially restored by anti-CD8beta Ab, and augmented in SPF mice bearing the TAP(-/-) genotype. Direct evidence for pDC cytolysis was obtained by rapid and selective pDC depletion in SPF mice transferred with RF CD8(+) T cells. These data indicate that commensal microbiota, via CTL activation, functionally shape systemic immune regulation that may modify risk of inflammatory disease.