Motoharu Suzuki

Distinct subsets of human invariant NKT cells differentially regulate T helper responses via dendritic cells

Invariant natural killer T (iNKT) cells regulate the T helper (Th) 1/2 balance and elicit either enhancement or suppression of the immune responses. However, the exact mechanism by which iNKT cells exert these contrasting functions has remained elusive. We demonstrate herein that two major distinct subsets of human iNKT cells, CD4+CD8β– (CD4+) and CD4–CD8β– (double negative; DN) cells, express functional CD40 ligand (CD40L), but they differentially regulate the dendritic cell (DC) function by reciprocal NKT‐DC interactions, thereby influencing the subsequent Th response. The CD4 subset stimulated by α‐galactosylceramide (α‐GalCer)‐loaded DC immediately produced massive amounts of IL‐4 and IL‐13, which together with IFN‐γ enhanced CD40L‐induced IL‐12 production by DC. In contrast, the DN subset eliminated the DC by cytolysis and changed the living DC into a default subtype, in turn markedly down‐regulating the levels of IL‐12. Therefore, the DC stimulated by the CD4 subset preferentially induced Th1 responses, whereas the DC reacted with the DN subset induced a shift toward Th2 responses. These findings may provide an important insight into better understanding the contribution of iNKT‐DC cross‐talk governing the Th1/2 balance and the diverse influences of iNKT cells in various diseases.

17β-Estradiol (E2) plus tumor necrosis factor-α induces a distorted maturation of human monocyte-derived dendritic cells and promotes their capacity to initiate T-helper 2 responses

There is growing evidence that 17 beta-estradiol (E2) modulates immune function. Recent studies indicated that certain effects of E2 on in vivo immune function are not a result of a direct action on T cells, but rather an indirect action on antigen-presenting cells. This study demonstrates that the pregnancy-associated doses of E2 plus tumor necrosis factor-alpha (TauNuF alpha) induce distorted maturation of human dendritic cells (DCs) that result in an increased capacity to induce T helper (Th) 2 responses. E2 did not affect the expression of human leukocyte antigen class II and costimulatory molecules by DCs, but elicited the ability of DC to produce CC chemokine ligand 1, which can attract CCR8-expressing Th2 cells and regulatory T cells. In addition, E2/TNF alpha-matured DCs increased the production of IL-10 relative to the IL-12p70 on CD40 ligation, thereby inducing naive T-cell differentiation into a Th2. Moreover, the increased concentration of E2 in the route of maturation did indeed further enhance Th2 deviation. The dominant Th2 deviation was induced at a high E2 concentration typical during pregnancy. These findings demonstrate that the high physiological levels of E2 may be an important endogenous component for regulating the DC function and skewing the immune response toward Th2.

Human chorionic gonadotropin confers resistance to oxidative stress–induced apoptosis in decidualizing human endometrial stromal cells

OBJECTIVE To investigate the effect of hCG on the expression of genes involved in oxidative stress resistance observed in decidualizing human endometrial stromal cells (HESCs). DESIGN In vitro experiment. SETTING Saitama Medical University hospital. PATIENT(S) Premenopausal women undergoing hysterectomy for myoma uteri. INTERVENTION(S) HESCs from hysterectomy specimens were isolated and incubated with 8-bromo-cyclic adenosine monophosphate and medroxyprogesterone acetate in the presence or absence of recombinant hCG (rhCG) at various concentrations. Hydrogen peroxide was used as the source of reactive oxygen species (ROS). MAIN OUTCOME MEASURE(S) Apoptotic cells, FOXO1, superoxide dismutase 2 (SOD2), Bax, and Bcl-2 protein expression. RESULT(S) In a dose-dependent manner, rhCG conferred additional protection to decidualizing HESCs against oxidative stress-induced apoptosis. In parallel, rhCG augmented the expression of the forkhead transcription factor FOXO1 and its downstream target, the ROS scavenger SOD2. rhCG also inhibited the expression of the proapoptotic Bax protein and up-regulated antiapoptotic Bcl-2 levels in decidualizing HESCs exposed to ROS. CONCLUSION(S) The data suggest that hCG might improve the uterine environment upon implantation by suppressing apoptotic responses in the maternal decidua under oxidative stress.

Role of human non-invariant NKT lymphocytes in the maintenance of type 2 T helper environment during pregnancy

The molecular and cellular mechanisms that generate the T(h)2 cytokine environment necessary for the maintenance of pregnancy are still not fully understood. We herein show that the human decidua is highly enriched for TCR alpha beta(+)CD161(+) NKT cells. They express non-invariant antigen receptors encoded by diverse TCRV alpha- and V beta-chain gene segments, thereby referred to as non-invariant NKT (non-iNKT) cells. In spite of their diverse TCR expression, they do not recognize fetal allo-antigens but specifically responded to CD1d-transfected cell lines. In contrast to the peripheral blood non-iNKT cells, the decidua-residing non-iNKT cells had a marked T(h)2 bias. In addition, they suppress the mixed leukocyte reaction directed against the paternal antigens. The T(h)2 cytokines have been known to stimulate trophoblast outgrowth and invasion. Thereby, the non-iNKT cells residing in the decidual tissue may have a functionally important interaction with the villous and extravillous trophoblast cells expressing CD1d and may therefore play a pivotal role in successful pregnancy by inhibiting fetal rejection and enhancing placental growth. These findings may reflect one mechanism that is an essential component for the T(h)2 environment necessary for the maintenance of pregnancy.

Cytokine-Dependent Modification of IL-12p70 and IL-23 Balance in Dendritic Cells by Ligand Activation of Vα24 Invariant NKT Cells

CD1d-restricted invariant NKT (iNKT) cells play crucial roles in various types of immune responses, including autoimmune diseases, infectious diseases and tumor surveillance. The mechanisms underlying their adjuvant functions are well understood. Nevertheless, although IL-4 and IL-10 production characterize iNKT cells able to prevent or ameliorate some autoimmune diseases and inflammatory conditions, the precise mechanisms by which iNKT cells exert immune regulatory function remain elusive. This study demonstrates that the activation of human iNKT cells by their specific ligand α-galactosylceramide enhances IL-12p70 while inhibiting the IL-23 production by monocyte-derived dendritic cells, and in turn down-regulating the IL-17 production by memory CD4+ Th cells. The ability of the iNKT cells to regulate the differential production of IL-12p70/IL-23 is mainly mediated by a remarkable hallmark of their function to produce both Th1 and Th2 cytokines. In particular, the down-regulation of IL-23 is markedly associated with a production of IL-4 and IL-10 from iNKT cells. Moreover, Th2 cytokines, such as IL-4 and IL-13 play a crucial role in defining the biased production of IL-12p70/IL-23 by enhancement of IL-12p70 in synergy with IFN-γ, whereas inhibition of the IFN-γ-promoted IL-23 production. Collectively, the results suggest that iNKT cells modify the IL-12p70/IL-23 balance to enhance the IL-12p70-induced cell-mediated immunity and suppress the IL-23-dependent inflammatory pathologies. These results may account for the long-appreciated contrasting beneficial and adverse consequence of ligand activation of iNKT cells.

Increased ovarian follicle atresia in obese Zucker rats is associated with enhanced expression of the forkhead transcription factor FOXO1

It is well established that hyperinsulinemia, resulting from insulin resistance, plays a role in the pathophysiology of polycystic ovary syndrome (PCOS). The aim of this study was to investigate if ovarian follicular development and atresia are impaired in obese hyperinsulinemic (fa/fa) Zucker rats. To gain insight into the molecular mechanism of follicular atresia, we also examined the expression and localization of forkhead transcription factor FOXO1, a major regulator of cell fate decisions such as differentiation, cell-cycle arrest, and cell death. Serum insulin but not gonadotropin levels were significantly higher in obese (fa/fa) rats when compared to lean controls. Total ovarian follicle number and the percentage of atretic follicles were also significantly increased in obese (fa/fa) rats. Follicle atresia was associated with nuclear accumulation of FOXO1 transcription factor in TUNEL-positive granulosa cells. These results suggest a role for FOXO1 in granulosa cell apoptosis and increased ovarian follicle atresia associated with hyperinsulinemia.

An algorithm for the management of coagulopathy from postpartum hemorrhage, using fibrinogen concentrate as first-line therapy

BACKGROUND We constructed an algorithm for the management of coagulopathy from massive postpartum hemorrhage. Fibrinogen concentrate was administered preferentially, and the dose of both fibrinogen concentrate and fresh frozen plasma given was determined by the plasma fibrinogen concentration and prothrombin time. The efficacy of the algorithm and the amount of fibrinogen concentrate and fresh frozen plasma transfused were determined. METHODS The study was conducted in a single teaching perinatal center. Nineteen patients were included between April 2011 and March 2014 (patient group). For a historical comparison group, we retrospectively analyzed the records of 19 patients who had been treated for coagulopathy from massive postpartum hemorrhage between April 2006 and March 2011 (control group). RESULTS Blood loss was significantly lower in the patient group. No adverse events were associated with this management in either group. The dose of fibrinogen concentrate administered was significantly higher and that of fresh frozen plasma administered was significantly lower in the patient group. CONCLUSION This algorithm appeared to help reduce blood loss and the total amount of fresh frozen plasma transfused when treating coagulopathy from postpartum hemorrhage, and may represent another strategy for achieving hemostasis in this setting.

Generation of mouse pluripotent stem cell-derived proliferating myeloid cells as an unlimited source of functional antigen-presenting cells.

Zhang and colleagues transduced c-Myc into mouse iPSC (induced pluripotent stem cells) to generate proliferating myeloid cells that propagate in a cytokine-dependent manner while retaining their potential to differentiate into functional antigen-presenting cells that stimulate tumor antigen-specific T-cell responses. The use of dendritic cells (DC) to prime tumor-associated antigen-specific T-cell responses provides a promising approach to cancer immunotherapy. Embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC) can differentiate into functional DCs, thus providing an unlimited source of DCs. However, the previously established methods of generating practical volumes of DCs from pluripotent stem cells (PSC) require a large number of PSCs at the start of the differentiation culture. In this study, we generated mouse proliferating myeloid cells (pMC) as a source of antigen-presenting cells (APC) using lentivirus-mediated transduction of the c-Myc gene into mouse PSC-derived myeloid cells. The pMCs could propagate almost indefinitely in a cytokine-dependent manner, while retaining their potential to differentiate into functional APCs. After treatment with IL4 plus GM-CSF, the pMCs showed impaired proliferation and differentiated into immature DC-like cells (pMC-DC) expressing low levels of major histocompatibility complex (MHC)-I, MHC-II, CD40, CD80, and CD86. In addition, exposure to maturation stimuli induced the production of TNFα and IL12p70, and enhanced the expression of MHC-II, CD40, and CD86, which is thus suggestive of typical DC maturation. Similar to bone marrow–derived DCs, they stimulated a primary mixed lymphocyte reaction. Furthermore, the in vivo transfer of pMC-DCs pulsed with H-2Kb-restricted OVA257-264 peptide primed OVA-specific cytotoxic T cells and elicited protection in mice against challenge with OVA-expressing melanoma. Overall, myeloid cells exhibiting cytokine-dependent proliferation and DC-like differentiation may be used to address issues associated with the preparation of DCs. Cancer Immunol Res; 3(6); 668–77. ©2015 AACR.