SHIP limits immunoregulatory capacity in the T-cell compartment

Abstract

Regulatory T cells (T regs) IntroductionRegulatory T cells (T regs ) actively mediate self-tolerance and thus control autoimmunity. 1,2 T regs also limit antitumor T-cell responses and deleterious allogeneic T-cell responses that cause graft-versushost disease (GVHD) 3,4 and solid organ allograft rejection, 5 making them valuable therapeutic targets. We previously found that donor and host allogeneic responses are compromised in SH2 domaincontaining inositol 5-phosphatase (SHIP)-deficient hosts, which exhibit significantly reduced acute rejection of MHC-mismatched bone marrow grafts and GVHD. 6,7 Thus, an immunosuppressive environment prevails in SHIP-deficient hosts. We consistently observe a profound expansion of myeloid suppressor cells (MySC) in SHIP-deficient mice. [6][7][8][9] Because host and donor T regs limit GVHD 4,10 and Mac1 ϩ Gr1 ϩ cells, similar to SHIP Ϫ/Ϫ MySC, expand T regs in tumor and GVHD models 11,12 ; we considered that the T reg compartment in SHIP-deficient hosts may also be expanded. In addition, SHIP deficiency could intrinsically effect T reg homeostasis and function. SHIP can oppose PI3K signaling pathways triggered by engagement of costimulatory and cytokine receptors critical for the suppressive function, survival, and expansion of T regs , such as CD25 (interleukin-2 receptor ␣), IL-7R, and OX40. [13][14][15] Because T regs were initially characterized as CD4 ϩ T cells coexpressing CD25, most T reg studies focus on this phenotype, which is shared with activated CD4 ϩ T cells. 16 To distinguish between T regs and activated T cells, molecular markers correlated with or obligate for T reg function have been identified, such as the transcription factor FoxP3, as well as surface markers CD103, glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) and OX40, among others. FoxP3 functions as the master regulator in the development and suppressive ability of T regs . 17 CD103 expression among CD4 ϩ CD25 ϩ T regs distinguishes an effector/memory-like subset that displays an inflammationseeking phenotype and exhibits greater suppressive capacity. 18,19 In addition, CD103, which binds E-cadherin, mediates the retention of CD103 ϩ lymphocyte in epithelial compartments, 19 which are major sites of GVHD. Thus, CD103 ϩ T regs might have a prominent role in the prevention against GVHD. GITR and OX40, members of the tumor necrosis factor receptor superfamily of receptors, are costimulatory molecules known to play key roles in promoting the homeostasis, expansion, and suppressive capability of T regs . 20,21 Furthermore, CD4 ϩ CD25 ϩ OX40 ϩ T regs represent a mature population that does not require preactivation or stimulation to suppress antigen-specific T-cell responses. 22 Analysis of CD103, GITR, and FoxP3 expression has allowed the identification of a T reg population among "naive" CD4 ϩ CD25 Ϫ T cells. Specifically, CD4 ϩ CD25 Ϫ CD103 ϩ T cells display regulatory activity in both an in vitro proliferation assay and in vivo disease models, such as colitis and antigen-ind...

Imbalanced signal transduction in regulatory T cells expressing the transcription factor FoxP3

“…3). Several reports also pointed to differences in Treg signaling architecture, such as a different involvement of PKC-Θ (18), DGKζ (19), SHIP (20), or Dlgh1 (21). Finally, there have been reports that signaling intensity downstream of TCR engagement is reduced in Treg relative to Tconv cells (22)(23)(24).…”

SHIP-1 inhibits CD95/APO-1/Fas-induced apoptosis in primary T lymphocytes and T leukemic cells by promoting CD95 glycosylation independently of its phosphatase activity

“…9,10,18,19 Peripheral T cells from SHIP-1 À/À mice are also constitutively activated and behave similar to T Reg cells. [18][19][20] However, T-cell-specific deletion of SHIP-1 did not lead to altered T-cell number, activation or emergence of T Reg cells, but instead revealed a role for SHIP-1 in the regulation of Th1/Th2 and cytotoxic responses. 40 It was proposed that the emergence of T Reg cells in mice bearing a germline mutation of SHIP-1 might be a consequence of the inflammatory environment in those mice rather than a T-cell defect as a result of SHIP-1 deletion.…”

“…9,10,18,19 Peripheral T cells from SHIP-1 À/À mice are also constitutively activated and behave similar to T Reg cells. [18][19][20] Given the phenotype of SHIP-1 À/À mice, we hypothesized that SHIP-1 could have different roles depending on the cell type. We postulate that unlike its well-known pro-apoptotic activity in myeloid and B cells, SHIP-1 has an anti-apoptotic function in T cells.…”

Preparation of Myeloid Derived Suppressor Cells (MDSC) from Naive and Pancreatic Tumor-bearing Mice using Flow Cytometry and Automated Magnetic Activated Cell Sorting (AutoMACS)

“…However, FACS sorting of viable MDSC from non-enriched, pooled leukocytes from tumor-bearing mice will require less time due to an increased abundance of MDSC percentages in response to tumor burden. It is important to note that sorted MDSC and other leukocytes can then be used in both functional assays such as mixed leukocyte reactions (MLR) 4 and in vivo adoptive transfer experiments 21 as well as in non-functional assays including qRT-PCR 22 , Western Blot 23 and cytospin/microscopy analyses 14 . Overall, this protocol can be modified for immunophenotyping and the enrichment of immunosuppressive and other leukocytes from lymphoid tissues or peripheral blood from mice, rat and humans to be used in a plethora of in vivo and in vitro assays.…”