Local Induction of Immunosuppressive CD8+ T Cells in the Gut-Associated Lymphoid Tissues

Background: In contrast to intestinal CD4 + regulatory T cells (Tregs), the generation and function of immunomodulatory intestinal CD8 + T cells is less well defined. To dissect the immunologic mechanisms of CD8 + T cell function in the mucosa, reactivity against hemagglutinin (HA) expressed in intestinal epithelial cells of mice bearing a MHC class-I-restricted T-cellreceptor specific for HA was studied. Methodology and Principal Findings: HA-specific CD8 + T cells were isolated from gut-associated tissues and phenotypically and functionally characterized for the expression of Foxp3 + and their suppressive capacity. We demonstrate that intestinal HA expression led to peripheral induction of HA-specific CD8 + Foxp3 + T cells. Antigen-experienced CD8 + T cells in this transgenic mouse model suppressed the proliferation of CD8 + and CD4 + T cells in vitro. Gene expression analysis of suppressive HA-specific CD8 + T cells revealed a specific up-regulation of CD103, Nrp1, Tnfrsf9 and Pdcd1, molecules also expressed on CD4 + T reg subsets. Finally, gut-associated dendritic cells were able to induce HA-specific CD8 + Foxp3 + T cells. Conclusion and Significance: We demonstrate that gut specific antigen presentation is sufficient to induce CD8 + T regs in vivo which may maintain intestinal homeostasis by down-modulating effector functions of T cells

In Situ Patrolling of Regulatory T Cells Is Essential for Protecting Autoimmune Exocrinopathy

BACKGROUND: Migration of T cells, including regulatory T (Treg) cells, into the secondary lymph organs is critically controlled by chemokines and adhesion molecules. However, the mechanisms by which Treg cells regulate organ-specific autoimmunity via these molecules remain unclear. Although we previously reported autoimmune exocrinopathy resembling Sjögren's syndrome (SS) in the lacrimal and salivary glands from C-C chemokine receptor 7 (CCR7)-deficient mice, it is still unclear whether CCR7 signaling might specifically affect the dynamics and functions of Treg cells in vivo. We therefore investigated the cellular mechanism for suppressive function of Treg cells via CCR7 in autoimmunity using mouse models and human samples. METHODS AND FINDINGS: Patrolling Treg cells were detected in the exocrine organs such as lacrimal and salivary glands from normal mice that tend to be targets for autoimmunity while the Treg cells were almost undetectable in the exocrine glands of CCR7(-/-) mice. In addition, we found the significantly increased retention of CD4(+)CD25(+)Foxp3(+) Treg cells in the lymph nodes of CCR7(-/-) mice with aging. Although Treg cell egress requires sphingosine 1-phosphate (S1P), chemotactic function to S1P of CCR7-/- Treg cells was impaired compared with that of WT Treg cells. Moreover, the in vivo suppression activity was remarkably diminished in CCR7(-/-) Treg cells in the model where Treg cells were co-transferred with CCR7(-/-) CD25(-)CD4(+) T cells into Rag2(-/-) mice. Finally, confocal analysis showed that CCR7(+)Treg cells were detectable in normal salivary glands while the number of CCR7(+)Treg cells was extremely decreased in the tissues from patients with Sjögren's syndrome. CONCLUSIONS: These results indicate that CCR7 essentially governs the patrolling functions of Treg cells by controlling the traffic to the exocrine organs for protecting autoimmunity. Characterization of this cellular mechanism could have clinical implications by supporting development of new diagnosis or treatments for the organ-specific autoimmune diseases such as Sjögren's syndrome and clarifying how the local immune system regulates autoimmunity

CD4(+)CD25(+) regulatory T cells inhibit the antigen-dependent expansion of self-reactive T cells in vivo

C1 - Journal Articles RefereedA deficiency of CD4+CD25+ regulatory T cells (CD25+ Tregs) in lymphopenic mice can result in the onset of autoimmune gastritis. The gastric H/K ATPase alpha (H/Kalpha) and beta (H/Kbeta) subunits are the immunodominant autoantigens recognized by effector CD4+ T cells in autoimmune gastritis. The mechanism by which CD25+ Tregs suppress autoimmune gastritis in lymphopenic mice is poorly understood. To investigate the antigenic requirements for the genesis and survival of gastritis-protecting CD25+ Tregs, we analyzed mice deficient in H/Kbeta and H/Kalpha, as well as a transgenic mouse line (H/Kbeta-tsA58 Tg line 224) that lacks differentiated gastric epithelial cells. By adoptive transfer of purified T cell populations to athymic mice, we show that the CD25+ Treg population from mice deficient in either one or both of H/Kalpha and H/Kbeta, or from the H/Kbeta-tsA58 Tg line 224 mice, is equally effective in suppressing the ability of polyclonal populations of effector CD4+ T cells to induce autoimmune gastritis. Furthermore, CD25+ Tregs, from either wild-type or H/Kalpha-deficient mice, dramatically reduced the expansion of pathogenic H/Kalpha-specific TCR transgenic T cells and the induction of autoimmune gastritis in athymic recipient mice. Proliferation of H/Kalpha-specific T cells in lymphopenic hosts occurs predominantly in the paragastric lymph node and was dependent on the presence of the cognate H/Kalpha Ag. Collectively, these studies demonstrate that the gastritis-protecting CD25+ Tregs do not depend on the major gastric Ags for their thymic development or their survival in the periphery, and that CD25+ Tregs inhibit the Ag-specific expansion of pathogenic T cells in vivo

Helios defines T cells being driven to tolerance in the periphery and thymus

The expression of the Ikaros transcription factor family member, Helios, has been shown to be associated with T-cell tolerance in both the thymus and the periphery. To better understand the importance of Helios in tolerance pathways, we have examined the expression of Helios in TCR-transgenic T cells specific for the gastric H(+) /K(+) ATPase, the autoantigen target in autoimmune gastritis. Analysis of H(+) /K(+) ATPase-specific T cells in mice with different patterns of H(+) /K(+) ATPase expression revealed that, in addition to the expression of Helios in CD4(+) Foxp3(+) regulatory T (Treg) cells, Helios is expressed by a large proportion of CD4(+) Foxp3(-) T cells in both the thymus and the paragastric lymph node (PgLN), which drains the stomach. In the thymus, Helios was expressed by H(+) /K(+) ATPase-specific thymocytes that were undergoing negative selection. In the periphery, Helios was expressed in H(+) /K(+) ATPase-specific CD4(+) T cells following H(+) /K(+) ATPase presentation and was more highly expressed when T-cell activation occurred in the absence of inflammation. Analysis of purified H(+) /K(+) ATPase-specific CD4(+) Foxp3(-) Helios(+) T cells demonstrated that they were functionally anergic. These results demonstrate that Helios is expressed by thymic and peripheral T cells that are being driven to tolerance in response to a genuine autoantigen

Thymic expression of a gastritogenic epitope results in positive selection of self-reactive pathogenic T cells

C1 - Journal Articles RefereedIntrathymic expression of tissue-specific self-Ags can mediate tolerance of self-reactive T cells. However, in this study we define circumstances by which thymic expression of a tissue-specific autoepitope enhances positive selection of disease-causing, self-reactive T cells. An immunodominant gastritogenic epitope, namely the gastric H/K ATPase beta subunit(253-277) (H/Kbeta(253-277)), was attached to the C terminus of the invariant chain (Ii) and the hybrid Ii (Ii-H/Kbeta(253-277)) expressed in mice under control of the Ii promoter. The Ii-H/Kbeta(253-277) fusion protein was localized to MHC class II-expressing cells in the thymus and periphery of Ii-H/Kbeta(253-277) transgenic mice. In one transgenic line the level of presentation in the periphery (spleen) was insufficient to activate naive, low affinity H/Kbeta(253-277)-specific transgenic T cells (1E4-TCR), whereas thymic presentation of H/Kbeta(253-277) enhanced positive selection of 1E4-TCR cells in Ii-H/Kbeta(253-277)/1E4-TCR double-transgenic mice. Furthermore, Ii-H/Kbeta(253-277)/1E4-TCR double-transgenic mice had an increased incidence of autoimmune gastritis compared with 1E4-TCR single-transgenic mice, demonstrating that the 1E4 T cells that seeded the periphery of Ii-H/Kbeta(253-277) mice were pathogenic. Therefore, low levels of tissue-specific Ags in the thymus can result in positive selection of low avidity, self-reactive T cells. These findings also suggest that the precise level of tissue-specific Ags in the thymus may be an important consideration in protection against autoimmune disease and that perturbation of the levels of self-Ags may be detrimental

The Golgi apparatus in the endomembrane-rich gastric parietal cells exist as functional stable mini-stacks dispersed throughout the cytoplasm

BACKGROUND INFORMATION: Acid-secreting gastric parietal cells are polarized epithelial cells that harbour highly abundant and specialized, H+,K+ ATPase-containing, tubulovesicular membranes in the apical cytoplasm. The Golgi apparatus has been implicated in the biogenesis of the tubulovesicular membranes; however, an unanswered question is how a typical Golgi organization could regulate normal membrane transport within the membrane-dense cytoplasm of parietal cells. RESULTS: Here, we demonstrate that the Golgi apparatus of parietal cells is not the typical juxta-nuclear ribbon of stacks, but rather individual Golgi units are scattered throughout the cytoplasm. The Golgi membrane structures labelled with markers of both cis- and trans-Golgi membrane, indicating the presence of intact Golgi stacks. The parietal cell Golgi stacks were closely aligned with the microtubule network and were shown to participate in both anterograde and retrograde transport pathways. Dispersed Golgi stacks were also observed in parietal cells from H+,K+ ATPase-deficient mice that lack tubulovesicular membranes. CONCLUSIONS: These results indicate that the unusual organization of individual Golgi stacks dispersed throughout the cytoplasm of these terminally differentiated cells is likely to be a developmentally regulated event