Creating transplant tolerance by taming adverse intragraft innate immunity

Certain forms of inflammation of an allograft are highly detrimental to the induction and maintenance of transplant tolerance as they foster stable commitment to graft-destructive, not graft-protective, forms of T-cell immunity. Hence, a reduction in adverse tissue inflammation may prove crucial in facilitating the induction and maintenance of a long-lasting state of transplant tolerance

Human CD4+ Memory T Cells Can Become CD4+IL-9+ T Cells

Background: IL-9 is a growth factor for T- and mast-cells that is secreted by human Th2 cells. We recently reported that IL-4+TGF-β directs mouse CD4+CD25−CD62L+ T cells to commit to inflammatory IL-9 producing CD4+ T cells. Methodology/Principal Findings: Here we show that human inducible regulatory T cells (iTregs) also express IL-9. IL-4+TGF-β induced higher levels of IL-9 expression in plate bound-anti-CD3 mAb (pbCD3)/soluble-anti-CD28 mAb (sCD28) activated human resting memory CD4+CD25−CD45RO+ T cells as compared to naïve CD4+CD25−CD45RA+ T cells. In addition, as compared to pbCD3/sCD28 plus TGF-β stimulation, IL-4+TGF-β stimulated memory CD4+CD25−CD45RO+ T cells expressed reduced FOXP3 protein. As analyzed by pre-amplification boosted single-cell real-time PCR, human CD4+IL-9+ T cells expressed GATA3 and RORC, but not IL-10, IL-13, IFNγ or IL-17A/F. Attempts to optimize IL-9 production by pbCD3/sCD28 and IL-4+TGF-β stimulated resting memory CD4+ T cells demonstrated that the addition of IL-1β, IL-12, and IL-21 further enhance IL-9 production. Conclusions/Significance: Taken together these data show both the differences and similarities between mouse and human CD4+IL9+ T cells and reaffirm the powerful influence of inflammatory cytokines to shape the response of activated CD4+ T cells to antigen

Hematopoietic Stem/Progenitor Cell Dependent Participation of Innate Lymphoid Cells in Low-Intensity Sterile Inflammation

Hematopoietic stem/progenitor cells (HSPC) are characterized by their unique capacities of self-renewal and multi-differentiation potential. This second property makes them able to adapt their differentiation profile depending on the local environment they reach. Taking advantage of an animal model of peritonitis, induced by injection of the TLR-2 ligand, zymosan, we sought to study the relationship between bone marrow-derived hematopoietic stem/progenitor cells (BM-HSPCs) and innate lymphoid cells (ILCs) regarding their emergence and differentiation at the site of inflammation. Our results demonstrate that the strength of the inflammatory signals affects the capacity of BM-derived HSPCs to migrate and give rise in situ to ILCs. Both low- and high-dose of zymosan injections trigger the appearance of mature ILCs in the peritoneal cavity where the inflammation occurs. Herein, we show that only in low-dose injected mice, the recovered ILCs are dependent on an in situ differentiation of BM-derived HSPCs and/or ILC2 precursors (ILC2P) wherein high-dose, the stronger inflammatory environment seems to be able to induce the emergence of ILCs independently of BM-derived HSPCs. We suggest that a relationship between HSPCs and ILCs seems to be affected by the strength of the inflammatory stimuli opening new perspectives in the manipulation of these early hematopoietic cells

Tracking Single Cells in Live Animals Using a Photoconvertible Near-Infrared Cell Membrane Label

We describe a novel photoconversion technique to track individual cells in vivo using a commercial lipophilic membrane dye, DiR. We show that DiR exhibits a permanent fluorescence emission shift (photoconversion) after light exposure and does not reacquire the original color over time. Ratiometric imaging can be used to distinguish photoconverted from non-converted cells with high sensitivity. Combining the use of this photoconvertible dye with intravital microscopy, we tracked the division of individual hematopoietic stem/progenitor cells within the calvarium bone marrow of live mice. We also studied the peripheral differentiation of individual T cells by tracking the gain or loss of FoxP3-GFP expression, a marker of the immune suppressive function of CD4+ T cells. With the near-infrared photoconvertible membrane dye, the entire visible spectral range is available for simultaneous use with other fluorescent proteins to monitor gene expression or to trace cell lineage commitment in vivo with high spatial and temporal resolution

Tim-2 regulates T helper type 2 responses and autoimmunity

Identification of the T cell immunoglobulin mucin-domain containing (Tim) gene family introduced a new family of cell surface molecules that is involved in the regulation of immune responses. We previously demonstrated that Tim-3 is expressed on terminally differentiated T helper (Th)1 cells, and serves to regulate Th1 immune responses. Here, we describe the identification and function of Tim-2, a novel member of the Tim gene family. In contrast with Tim-3, we demonstrate that Tim-2 is expressed preferentially in differentiated Th2 cells. Blockade of the Tim-2/Tim-2 ligand interaction, by administration of soluble Tim-2 fusion protein (Tim-2 immunoglobulin [Ig]), results in T cell hyperproliferation and the production of Th2 cytokines. Administration of Tim-2 Ig during the induction phase reduces the severity of experimental autoimmune encephalomyelitis, a Th1-mediated autoimmune disease model of multiple sclerosis. We propose that Tim-2, an orthologue of human Tim-1, is critical for the regulation of Th2 responses during autoimmune inflammation

Adenosine generation catalyzed by CD39 and CD73 expressed on regulatory T cells mediates immune suppression

The study of T regulatory cells (T reg cells) has been limited by the lack of specific surface markers and an inability to define mechanisms of suppression. We show that the expression of CD39/ENTPD1 in concert with CD73/ecto-5′-nucleotidase distinguishes CD4+/CD25+/Foxp3+ T reg cells from other T cells. These ectoenzymes generate pericellular adenosine from extracellular nucleotides. The coordinated expression of CD39/CD73 on T reg cells and the adenosine A2A receptor on activated T effector cells generates immunosuppressive loops, indicating roles in the inhibitory function of T reg cells. Consequently, T reg cells from Cd39-null mice show impaired suppressive properties in vitro and fail to block allograft rejection in vivo. We conclude that CD39 and CD73 are surface markers of T reg cells that impart a specific biochemical signature characterized by adenosine generation that has functional relevance for cellular immunoregulation