Following the fate of one insulin-reactive CD4 T cell: conversion into Teffs and Tregs in the periphery controls diabetes in NOD mice.

Type 1 Diabetes Center, La Jolla Institute for Allergy and Immunology, La Jolla, California, USA.
Diabetes (Impact Factor: 8.47). 03/2012; 61(5):1169-79. DOI: 10.2337/db11-0671
Source: PubMed

ABSTRACT In diabetic patients and susceptible mice, insulin is a targeted autoantigen. Insulin B chain 9-23 (B:9-23) autoreactive CD4 T cells are key for initiating autoimmune diabetes in NOD mice; however, little is known regarding their origin and function. To this end, B:9-23-specific, BDC12-4.1 T-cell receptor (TCR) transgenic (Tg) mice were studied, of which, despite expressing a single TCR on the recombination activating gene-deficient background, only a fraction develops diabetes in an asynchronous manner. BDC12-4.1 CD4 T cells convert into effector (Teff) and Foxp3(+)-expressing adaptive regulatory T cells (aTregs) soon after leaving the thymus as a result of antigen recognition and homeostatic proliferation. The generation of aTreg causes the heterogeneous diabetes onset, since crossing onto the scurfy (Foxp3) mutation, BDC12-4.1 TCR Tg mice develop accelerated and fully penetrant diabetes. Similarly, adoptive transfer and bone marrow transplantation experiments showed differential diabetes kinetics based on Foxp3(+) aTreg's presence in the BDC12-4.1 donors. A single-specificity, insulin-reactive TCR escapes thymic deletion and simultaneously converts into aTreg and Teff, establishing an equilibrium that determines diabetes penetrance. These results are of particular importance for understanding disease pathogenesis. They suggest that once central tolerance is bypassed, autoreactive cells arriving in the periphery do not by default follow solely a pathogenic fate upon activation.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Autoreactive T cells infiltrating the target organ can possess a broad TCR affinity range. However, the extent to which such biophysical parameters contribute to T cell pathogenic potential remains unclear. In this study, we selected eight InsB9-23-specific TCRs cloned from CD4(+) islet-infiltrating T cells that possessed a relatively broad range of TCR affinity to generate NOD TCR retrogenic mice. These TCRs exhibited a range of two-dimensional affinities (∼10(-4)-10(-3) μm(4)) that correlated with functional readouts and responsiveness to activation in vivo. Surprisingly, both higher and lower affinity TCRs could mediate potent insulitis and autoimmune diabetes, suggesting that TCR affinity does not exclusively dictate or correlate with diabetogenic potential. Both central and peripheral tolerance mechanisms selectively impinge on the diabetogenic potential of high-affinity TCRs, mitigating their pathogenicity. Thus, TCR affinity and multiple tolerance mechanisms converge to shape and broaden the diabetogenic T cell repertoire, potentially complicating efforts to induce broad, long-term tolerance.
    The Journal of Immunology 06/2014; 193(2). DOI:10.4049/jimmunol.1400043 · 5.36 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The infusion of ex vivo-expanded autologous T regulatory (Treg) cells is potentially an effective immunotherapeutic strategy against graft-versus-host disease (GvHD) and several autoimmune diseases, such as type 1 diabetes (T1D). However, in vitro differentiation of antigen-specific T cells into functional and stable Treg (iTreg) cells has proved challenging. As insulin is the major autoantigen leading to T1D, we tested the capacity of insulin-specific T-cell receptor (TCR) transgenic CD4+ T cells of the BDC12-4.1 clone to convert into Foxp3+ iTreg cells. We found that in vitro polarization toward Foxp3+ iTreg was effective with a majority (>70%) of expanded cells expressing Foxp3. However, adoptive transfer of Foxp3+ BDC12-4.1 cells did not prevent diabetes onset in immunocompetent NOD mice. Thus, in vitro polarization of insulin-specific BDC12-4.1 TCR transgenic CD4+ T cells toward Foxp3+ cells did not provide dominant tolerance in recipient mice. These results highlight the disconnect between an in vitro acquired Foxp3+ cell phenotype and its associated in vivo regulatory potential.
    PLoS ONE 11/2014; 9(11):e112242. DOI:10.1371/journal.pone.0112242 · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Protein tyrosine phosphatases (PTPs) regulate T-cell receptor (TCR) signaling and thus have a role in T-cell differentiation. Here we tested whether the autoimmune predisposing gene PTPN22 encoding for a PTP that inhibits TCR signaling, affects the generation of FOXP3(+) T regulatory (Treg) cells and Th1 cells. Murine CD4(+) T cells isolated from Ptpn22 knockout (KO) mice, cultured in Treg-cell-polarizing conditions showed increased sensitivity to TCR activation as compared to wild-type (WT) cells and subsequently, reduced FOXP3 expression at optimal-to-high levels of activation. At lower levels of TCR activation however, Ptpn22(KO) CD4(+) T cells showed enhanced expression of FOXP3. Similar experiments in humans revealed that at optimal levels of TCR activation, PTPN22 knockdown by specific oligonucleotides compromises the differentiation of naïve CD4(+) T cells into Treg cells. Notably, in vivo Treg-cell conversion experiments in mice showed delayed kinetic but overall increased frequency and number of Treg in the absence of Ptpn22. In contrast, the in vitro and in vivo generation of Th1 cells was comparable between WT and Ptpn22(KO) mice, thus suggesting PTPN22 as a FOXP3-specific regulating factor. Altogether, these results propose PTPN22 as key factor in setting the proper threshold for FOXP3(+) Treg-cell differentiation.
    Clinical & Experimental Immunology 06/2014; 178(1). DOI:10.1111/cei.12393 · 3.28 Impact Factor