Description: CD4 + T cells developing toward a Th2 fate express IL-4, IL-5, and IL-13 while inhibiting production of cytokines associated with other Th types, such as the Th1 cytokine IFN- . IL-4–producing Th2 effector cells give rise to a long-lived memory population committed to reactivation of the Th2 cytokine gene expression program. However, reactivation of these effector-derived cells under Th1-skewing conditions leads to production of IFN- along with IL-4 in the same cell. We now show that this flexibility ("plasticity") of cytokine expression is preceded by a loss of the repressive DNA methylation of the Ifng promoter acquired during Th2 polarization yet requires STAT4 along with T-box expressed in T cells. Surprisingly, loss of either STAT4 or T-box expressed in T cells increased Ifng promoter CpG methylation in both effector and memory Th2 cells. Taken together, our data suggest a model in which the expression of IFN- by Th2-derived memory cells involves attenuation of epigenetic repression in memory Th2 cells, combined with Th1-polarizing signals after their recall activation.

Description: 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-2Rα and IL-7Rα. 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.

Description: Hiromi Kubagawa and John E. Coligan coordinated an online meeting to define an appropriate nomenclature for the cell surface glycoprotein presently designated by different names: Toso, Fas apoptosis inhibitory molecule 3 (FAIM3), and IgM FcR (FcμR). FAIM3 and Faim3 are the currently approved symbols for the human and mouse genes, respectively, in the National Center for Biotechnology Information, Ensembl, and other databases. However, recent functional results reported by several groups of investigators strongly support a recommendation for renaming FAIM3/Faim3 as FCMR/Fcmr, a name better reflecting its physiological function as the FcR for IgM. Participants included 12 investigators involved in studying Toso/FAIM3(Faim3)/FμR, representatives from the Human Genome Nomenclature Committee (Ruth Seal) and the Mouse Genome Nomenclature Committee (Monica McAndrews), and an observer from the IgM research field (Michael Carroll). In this article, we provide a brief background of the key research on the Toso/FAIM3(Faim3)/FcμR proteins, focusing on the ligand specificity and functional activity, followed by a brief summary of discussion about adopting a single name for this molecule and its gene and a resulting recommendation for genome nomenclature committees.

Description: In health, long-lived plasma cells (LLPC) are essential for durable protective humoral immunity, and, conversely, in disease are a major source of pathogenic Abs in autoimmunity, graft rejection, and allergy. However, the molecular basis for their longevity is largely unknown. We have recently found that CD28 signaling in plasma cells (PC) is essential for sustaining Ab titers, by supporting the survival of LLPC, but not short-lived PC (SLPC). We now find that, unlike SLPC, CD28 activation in LLPC induces prosurvival downstream Vav signaling. Knockin mice with CD28 cytoplasmic tail mutations that abrogate Vav signaling (CD28-AYAA) had significantly fewer LLPC but unaffected SLPC numbers, whereas mice with mutations that abrogate PI3K signaling (CD28-Y170F) were indistinguishable from wild-type controls. This was consistent with the loss of CD28’s prosurvival effect in LLPC from CD28-AYAA, but not CD28-Y170F, mice. Furthermore, the CD28 Vav motif in the B lineage was essential for the long-term maintenance of Ag-specific LLPC populations and Ab titers in vivo. Signaling downstream of the CD28 Vav motif induced previously undescribed transcriptional regulation of B lymphocyte–induced maturation protein-1, a key mediator of PC differentiation and maintenance. These findings suggest CD28 signaling in LLPC modulates the central B lymphocyte–induced maturation protein-1 transcriptional nexus involved in long-term survival and function.

Description: IL-6 is a major causative factor of inflammatory disease. Although IL-6 and its signaling pathways are promising targets, orally available small-molecule drugs specific for IL-6 have not been developed. To discover IL-6 antagonists, we screened our in-house chemical library and identified LMT-28, a novel synthetic compound, as a candidate IL-6 blocker. The activity, mechanism of action, and direct molecular target of LMT-28 were investigated. A reporter gene assay showed that LMT-28 suppressed activation of STAT3 induced by IL-6, but not activation induced by leukemia inhibitory factor. In addition, LMT-28 downregulated IL-6–stimulated phosphorylation of STAT3, gp130, and JAK2 protein and substantially inhibited IL-6–dependent TF-1 cell proliferation. LMT-28 antagonized IL-6–induced TNF-α production in vivo. In pathologic models, oral administration of LMT-28 alleviated collagen-induced arthritis and acute pancreatitis in mice. Based on the observation of upstream IL-6 signal inhibition by LMT-28, we hypothesized IL-6, IL-6Rα, or gp130 to be putative molecular targets. We subsequently demonstrated direct interaction of LMT-28 with gp130 and specific reduction of IL-6/IL-6Rα complex binding to gp130 in the presence of LMT-28, which was measured by surface plasmon resonance analysis. Taken together, our data suggest that LMT-28 is a novel synthetic IL-6 inhibitor that functions through direct binding to gp130.

Description: Peroxiredoxin (Prx) II is an intracellular antioxidant molecule that eliminates hydrogen peroxide, employing a high substrate-binding affinity. PrxII deficiency increases the levels of intracellular reactive oxygen species in many types of cells, which may increase reactive oxygen species–mediated inflammation. In this study, we investigated the susceptibility of PrxII knockout (KO) mice to experimentally induced colitis and the effects of PrxII on the immune system. Wild-type mice displayed pronounced weight loss, high mortality, and colon shortening after dextran sulfate sodium administration, whereas colonic inflammation was significantly attenuated in PrxII KO mice. Although macrophages were hyperactivated in PrxII KO mice, the amount of IFN- and IL-17 produced by CD4 + T cells was substantially reduced. Foxp3 + regulatory T (Treg) cells were elevated, and Foxp3 protein expression was increased in the absence of PrxII in vitro and in vivo. Restoration of PrxII into KO cells suppressed the increased Foxp3 expression. Interestingly, endogenous PrxII was inactivated through hyperoxidation during Treg cell development. Furthermore, PrxII deficiency stabilized FoxO1 expression by reducing mouse double minute 2 homolog expression and subsequently activated FoxO1-mediated Foxp3 gene transcription. PrxII overexpression, in contrast, reduced FoxO1 and Foxp3 expression. More interestingly, adoptive transfer of naive CD4 + T cells from PrxII KO mice into immune-deficient mice attenuated T cell–induced colitis, with a reduction in mouse double minute 2 homolog expression and an increase in FoxO1 and Foxp3 expression. These results suggest that inactivation of PrxII is important for the stability of FoxO1 protein, which subsequently mediates Foxp3 + Treg cell development, thereby attenuating colonic inflammation.

Description: The CD27–CD70 pathway is known to provide a costimulatory signal, with CD70 expressed on APCs and CD27 functions on T cells. Although CD70 is also expressed on activated T cells, it remains unclear how T cell–derived CD70 affects T cell function. Therefore, we have assessed the role of T cell–derived CD70 using adoptive-transfer models, including autoimmune inflammatory bowel disease and allogeneic graft-versus-host disease. Surprisingly, compared with wild-type T cells, CD70 –/– T cells caused more severe inflammatory bowel disease and graft-versus-host disease and produced higher levels of inflammatory cytokines. Mechanistic analyses reveal that IFN- induces CD70 expression in T cells, and CD70 limits T cell expansion via a regulatory T cell–independent mechanism that involves caspase-dependent T cell apoptosis and upregulation of inhibitory immune checkpoint molecules. Notably, T cell–intrinsic CD70 signaling contributes, as least in part, to the inhibitory checkpoint function. Overall, our findings demonstrate for the first time, to our knowledge, that T cell–derived CD70 plays a novel immune checkpoint role in inhibiting inflammatory T cell responses. This study suggests that T cell–derived CD70 performs a critical negative feedback function to downregulate inflammatory T cell responses.

Description: Chemokines have been shown to be essential players in a range of cancer contexts. In this study, we demonstrate that mice deficient in the atypical chemokine receptor Ackr2 display impaired development of metastasis in vivo in both cell line and spontaneous models. Further analysis reveals that this relates to increased expression of the chemokine receptor CCR2, specifically by KLRG1 + NK cells from the Ackr2 –/– mice. This leads to increased recruitment of KLRG1 + NK cells to CCL2-expressing tumors and enhanced tumor killing. Together, these data indicate that Ackr2 limits the expression of CCR2 on NK cells and restricts their tumoricidal activity. Our data have important implications for our understanding of the roles for chemokines in the metastatic process and highlight Ackr2 and CCR2 as potentially manipulable therapeutic targets in metastasis.

Description: The anti-proliferative agent hexamethylene bisacetamide (HMBA) belongs to a class of hybrid bipolar compounds developed more than 30 y ago for their ability to induce terminal differentiation of transformed cells. Recently, HMBA has also been shown to trigger HIV transcription from latently infected cells, via a CDK9/HMBA inducible protein-1 dependent process. However, the effect of HMBA on the immune response has not been explored. We observed that pretreatment of human peripheral blood mononuclear cells with HMBA led to a markedly increased production of IL-12 and IFN-, but not of TNF-α, IL-6, and IL-8 upon subsequent infection with Burkholderia pseudomallei and Salmonella enterica . HMBA treatment was also associated with better intracellular bacterial control. HMBA significantly improved IL-12p70 production from CD14 + monocytes during infection partly via the induction of type I IFN in these cells, which primed an increased transcription of the p35 subunit of IL-12p70 during infection. HMBA also increased early type I IFN transcription in human monocytic and epithelial cell lines, but this was surprisingly independent of its previously reported effects on positive transcription elongation factor b and HMBA inducible protein-1. Instead, the effect of HMBA was downstream of a calcium influx, and required the pattern recognition receptor and adaptor STING but not cGAS. Our work therefore links the STING-IRF3 axis to enhanced IL-12 production and intracellular bacterial control in primary monocytes. This raises the possibility that HMBA or related small molecules may be explored as therapeutic adjuvants to improve disease outcomes during intracellular bacterial infections.

Description: CD83 is a member of the Ig gene superfamily, first identified in activated lymphocytes. Since then, CD83 has become an important marker for defining activated human dendritic cells (DC). Several potential CD83 mRNA isoforms have been described, including a soluble form detected in human serum, which may have an immunosuppressive function. To further understand the biology of CD83, we examined its expression in different human immune cell types before and after activation using a panel of mouse and human anti-human CD83 mAb. The mouse anti-human CD83 mAbs, HB15a and HB15e, and the human anti-human CD83 mAb, 3C12C, were selected to examine cytoplasmic and surface CD83 expression, based on their different binding characteristics. Glycosylation of CD83, the CD83 mRNA isoforms, and soluble CD83 released differed among blood DC, monocytes, and monocyte-derived DC, and other immune cell types. A small T cell population expressing surface CD83 was identified upon T cell stimulation and during allogeneic MLR. This subpopulation appeared specifically during viral Ag challenge. We did not observe human CD83 on unstimulated human natural regulatory T cells (Treg), in contrast to reports describing expression of CD83 on mouse Treg. CD83 expression was increased on CD4 + , CD8 + T, and Treg cells in association with clinical acute graft-versus-host disease in allogeneic hematopoietic cell transplant recipients. The differential expression and function of CD83 on human immune cells reveal potential new roles for this molecule as a target of therapeutic manipulation in transplantation, inflammation, and autoimmune diseases.