INVIVOMAB ANTI-MOUSE IL-7RΑ (CD127) (CLONE: A7R34)

Becker, A. M., et al. (2015). “ADAM17 limits the expression of CSF1R on murine hematopoietic progenitors.” Exp Hematol 43(1): 44-52 e41-43. PubMed

All-lymphoid progenitors (ALPs) yield few myeloid cells in vivo, but readily generate such cells in vitro. The basis for this difference remains unknown. We hypothesized that ALPs limit responsiveness to in vivo concentrations of myeloid-promoting cytokines by reducing expression of the corresponding receptors, potentially through posttranscriptional mechanisms. Consistent with such a mechanism, ALPs express higher levels of CSF1R transcripts than their upstream precursors, yet show limited cell-surface protein expression of colony-stimulating factor 1 receptor (CSF1R). All-lymphoid progenitors and other hematopoietic progenitors deficient in A disintegrin and metalloproteinase domain 17 (ADAM17), display elevated cell surface CSF1R expression. ADAM17(-/-) ALPs, however, fail to yield myeloid cells upon transplantation into irradiated recipients. Moreover, ADAM17(-/-) ALPs yield fewer macrophages in vitro than control ALPs at high concentrations of macrophage colony stimulating factor. Mice with hematopoietic-specific deletion of ADAM17 have normal numbers of myeloid and lymphoid progenitors and mature cells in vivo. These data demonstrate that ADAM17 limits CSF1R protein expression on hematopoietic progenitors, but that compensatory mechanisms prevent elevated CSF1R levels from altering lymphoid progenitor potential.

Goossens, S., et al. (2015). “ZEB2 drives immature T-cell lymphoblastic leukaemia development via enhanced tumour-initiating potential and IL-7 receptor signalling.” Nat Commun 6: 5794. PubMed

Early T-cell precursor leukaemia (ETP-ALL) is a high-risk subtype of human leukaemia that is poorly understood at the molecular level. Here we report translocations targeting the zinc finger E-box-binding transcription factor ZEB2 as a recurrent genetic lesion in immature/ETP-ALL. Using a conditional gain-of-function mouse model, we demonstrate that sustained Zeb2 expression initiates T-cell leukaemia. Moreover, Zeb2-driven mouse leukaemia exhibit some features of the human immature/ETP-ALL gene expression signature, as well as an enhanced leukaemia-initiation potential and activated Janus kinase (JAK)/signal transducers and activators of transcription (STAT) signalling through transcriptional activation of IL7R. This study reveals ZEB2 as an oncogene in the biology of immature/ETP-ALL and paves the way towards pre-clinical studies of novel compounds for the treatment of this aggressive subtype of human T-ALL using our Zeb2-driven mouse model.

Torow, N., et al. (2015). “Active suppression of intestinal CD4(+)TCRalphabeta(+) T-lymphocyte maturation during the postnatal period.” Nat Commun 6: 7725. PubMed

Priming of the mucosal immune system during the postnatal period substantially influences host-microbial interaction and susceptibility to immune-mediated diseases in adult life. The underlying mechanisms are ill defined. Here we show that shortly after birth, CD4 T cells populate preformed lymphoid structures in the small intestine and quickly acquire a distinct transcriptional profile. T-cell recruitment is independent of microbial colonization and innate or adaptive immune stimulation but requires beta7 integrin expression. Surprisingly, neonatal CD4 T cells remain immature throughout the postnatal period under homeostatic conditions but undergo maturation and gain effector function on barrier disruption. Maternal SIgA and regulatory T cells act in concert to prevent immune stimulation and maintain the immature phenotype of CD4 T cells in the postnatal intestine during homeostasis. Active suppression of CD4 T-cell maturation during the postnatal period might contribute to prevent auto-reactivity, sustain a broad TCR repertoire and establish life-long immune homeostasis.

Devarajan, P., et al. (2014). “Opposing effects of CTLA4 insufficiency on regulatory versus conventional T cells in autoimmunity converge on effector memory in target tissue.” J Immunol 193(9): 4368-4380. PubMed

Quantitative variations in CTLA4 expression, because of genetic polymorphisms, are associated with various human autoimmune conditions, including type 1 diabetes (T1D). Extensive studies have demonstrated that CTLA4 is not only essential for the suppressive role of regulatory T cells (T(reg)) but also required for intrinsic control of conventional T (T(conv)) cells. We report that a modest insufficiency of CTLA4 in mice, which mimics the effect of some human CTLA4 genetic polymorphisms, accompanied by a T1D-permissive MHC locus, was sufficient to induce juvenile-onset diabetes on an otherwise T1D-resistant genetic background. Reduction in CTLA4 levels had an unanticipated effect in promoting Treg function both in vivo and in vitro. It led to an increase in T(reg) memory in both lymphoid and nonlymphoid target tissue. Conversely, modulating CTLA4 by either RNA interference or Ab blockade promoted conventional effector memory T cell formation in the T(conv) compartment. The CD4(+) conventional effector memory T cells, including those within target tissue, produced IL-17 or IFN-gamma. Blocking IL-7 signaling reduced the Th17 autoimmune compartment but did not suppress the T1D induced by CTLA4 insufficiency. Enhanced effector memory formation in both T(conv) and T(reg) lineages may underpin the apparently dichotomized impact of CTLA4 insufficiency on autoimmune pathogenesis. Therefore, although the presence of CTLA4 plays a critical role in controlling homeostasis of T cells, its quantitative variation may impose diverse or even opposing effects on distinct lineages of T cells, an optimal sum of which is necessary for preservation of T cell immunity while suppressing tissue damage.

Le Saout, C., et al. (2014). “Chronic exposure to type-I IFN under lymphopenic conditions alters CD4 T cell homeostasis.” PLoS Pathog 10(3): e1003976. PubMed

HIV infection and the associated chronic immune activation alter T cell homeostasis leading to CD4 T cell depletion and CD8 T cell expansion. The mechanisms behind these outcomes are not totally defined and only partially explained by the direct cytopathic effect of the virus. In this manuscript, we addressed the impact of lymphopenia and chronic exposure to IFN-alpha on T cell homeostasis. In a lymphopenic murine model, this interaction led to decreased CD4 counts and CD8 T cell expansion in association with an increase in the Signal Transducer and Activator of Transcription 1 (STAT1) levels resulting in enhanced CD4 T cell responsiveness to IFN-alpha. Thus, in the setting of HIV infection, chronic stimulation of this pathway could be detrimental for CD4 T cell homeostasis.

McKinstry, K. K., et al. (2014). “Effector CD4 T-cell transition to memory requires late cognate interactions that induce autocrine IL-2.” Nat Commun 5: 5377. PubMed

It is unclear how CD4 T-cell memory formation is regulated following pathogen challenge, and when critical mechanisms act to determine effector T-cell fate. Here, we report that following influenza infection most effectors require signals from major histocompatibility complex class II molecules and CD70 during a late window well after initial priming to become memory. During this timeframe, effector cells must produce IL-2 or be exposed to high levels of paracrine or exogenously added IL-2 to survive an otherwise rapid default contraction phase. Late IL-2 promotes survival through acute downregulation of apoptotic pathways in effector T cells and by permanently upregulating their IL-7 receptor expression, enabling IL-7 to sustain them as memory T cells. This new paradigm defines a late checkpoint during the effector phase at which cognate interactions direct CD4 T-cell memory generation.

Gratz, I. K., et al. (2013). “Cutting Edge: memory regulatory t cells require IL-7 and not IL-2 for their maintenance in peripheral tissues.” J Immunol 190(9): 4483-4487. PubMed

Thymic Foxp3-expressing regulatory T cells are activated by peripheral self-antigen to increase their suppressive function, and a fraction of these cells survive as memory regulatory T cells (mTregs). mTregs persist in nonlymphoid tissue after cessation of Ag expression and have enhanced capacity to suppress tissue-specific autoimmunity. In this study, we show that murine mTregs express specific effector memory T cell markers and localize preferentially to hair follicles in skin. Memory Tregs express high levels of both IL-2Ralpha and IL-7Ralpha. Using a genetic-deletion approach, we show that IL-2 is required to generate mTregs from naive CD4(+) T cell precursors in vivo. However, IL-2 is not required to maintain these cells in the skin and skin-draining lymph nodes. Conversely, IL-7 is essential for maintaining mTregs in skin in the steady state. These results elucidate the fundamental biology of mTregs and show that IL-7 plays an important role in their survival in skin.

Satpathy, A. T., et al. (2013). “Notch2-dependent classical dendritic cells orchestrate intestinal immunity to attaching-and-effacing bacterial pathogens.” Nat Immunol 14(9): 937-948. PubMed

Defense against attaching-and-effacing bacteria requires the sequential generation of interleukin 23 (IL-23) and IL-22 to induce protective mucosal responses. Although CD4(+) and NKp46(+) innate lymphoid cells (ILCs) are the critical source of IL-22 during infection, the precise source of IL-23 is unclear. We used genetic techniques to deplete mice of specific subsets of classical dendritic cells (cDCs) and analyzed immunity to the attaching-and-effacing pathogen Citrobacter rodentium. We found that the signaling receptor Notch2 controlled the terminal stage of cDC differentiation. Notch2-dependent intestinal CD11b(+) cDCs were an obligate source of IL-23 required for survival after infection with C. rodentium, but CD103(+) cDCs dependent on the transcription factor Batf3 were not. Our results demonstrate a nonredundant function for CD11b(+) cDCs in the response to pathogens in vivo.

Ashbaugh, J. J., et al. (2013). “IL7Ralpha contributes to experimental autoimmune encephalomyelitis through altered T cell responses and nonhematopoietic cell lineages.” J Immunol 190(9): 4525-4534. PubMed

A mutation in the IL7Ralpha locus has been identified as a risk factor for multiple sclerosis (MS), a neurodegenerative autoimmune disease characterized by inflammation, demyelination, and axonal damage. IL7Ralpha has well documented roles in lymphocyte development and homeostasis, but its involvement in disease is largely understudied. In this study, we use the experimental autoimmune encephalomyelitis (EAE) model of MS to show that a less severe form of the disease results when IL7Ralpha expression is largely restricted to thymic tissue in IL7RTg(IL7R-/-) mice. Compared with wild-type (WT) mice, IL7RTg(IL7R-/-) mice exhibited reduced paralysis and myelin damage that correlated with dampened effector responses, namely decreased TNF production. Furthermore, treatment of diseased WT mice with neutralizing anti-IL7Ralpha Ab also resulted in significant improvement of EAE. In addition, chimeric mice were generated by bone marrow transplant to limit expression of IL7Ralpha to cells of either hematopoietic or nonhematopoietic origin. Mice lacking IL7Ralpha only on hematopoietic cells develop severe EAE, suggesting that IL7Ralpha expression in the nonhematopoietic compartment contributes to disease. Moreover, novel IL7Ralpha expression was identified on astrocytes and oligodendrocytes endogenous to the CNS. Chimeric mice that lack IL7Ralpha only on nonhematopoietic cells also develop severe EAE, which further supports the role of IL7Ralpha in T cell effector function. Conversely, mice that lack IL7Ralpha throughout both compartments are dramatically protected from disease. Taken together, these data indicate that multiple cell types use IL7Ralpha signaling in the development of EAE, and inhibition of this pathway should be considered as a new therapeutic avenue for MS.

Chougnet, C. A., et al. (2011). “A major role for Bim in regulatory T cell homeostasis.” J Immunol 186(1): 156-163. PubMed

We have previously shown that regulatory T cells (Treg) accumulate dramatically in aged animals and negatively impact the ability to control persistent infection. However, the mechanisms underlying the age-dependent accrual of Treg remain unclear. In this study, we show that Treg accumulation with age is progressive and likely not the result of increased thymic output, increased peripheral proliferation, or from enhanced peripheral conversion. Instead, we found that Treg from aged mice are more resistant to apoptosis than Treg from young mice. Although Treg from aged mice had increased expression of functional IL-7Ralpha, we found that IL-7R signaling was not required for maintenance of Treg in vivo. Notably, aged Treg exhibit decreased expression of the proapoptotic molecule Bim compared with Treg from young mice. Furthermore, in the absence of Bim, Treg accumulate rapidly, accounting for >25% of the CD4(+) T cell compartment by 6 mo of age. Additionally, accumulation of Treg in Bim-deficient mice occurred after the cells left the transitional recent thymic emigrant compartment. Mechanistically, we show that IL-2 drives preferential proliferation and accumulation of Bim(lo) Treg. Collectively, our data suggest that chronic stimulation by IL-2 leads to preferential expansion of Treg having low expression of Bim, which favors their survival and accumulation in aged hosts.