GATA3 induces the pathogenicity of Th17 cells via regulating GM-CSF expression

T-bet-expressing Th17 (T-bet+RORγt+) cells are associated with the induction of pathology during experimental autoimmune encephalomyelitis (EAE) and the encephalitic nature of these Th17 cells can be explained by their ability to produce GM-CSF. However, the upstream regulatory mechanisms that control Csf2 (gene encoding GM-CSF) expression are still unclear. In this study, we found that Th17 cells dynamically expressed GATA3, the master transcription factor for Th2 cell differentiation, during their differentiation both in vitro and in vivo. Early deletion of Gata3 in three complimentary conditional knockout models by Cre-ERT2, hCd2 Cre and Tbx21 Cre, respectively, limited the pathogenicity of Th17 cells during EAE, which was correlated with a defect in generating pathogenic T-bet-expressing Th17 cells. These results indicate that early GATA3-dependent gene regulation is critically required to generate a de novo encephalitogenic Th17 response. Furthermore, a late deletion of Gata3 via Cre-ERT2 in the adoptive transfer EAE model resulted in a cell intrinsic failure to induce EAE symptoms which was correlated with a substantial reduction in GM-CSF production without affecting the generation and/or maintenance of T-bet-expressing Th17 cells. RNA-Seq analysis of Gata3-sufficient and Gata3-deficient CNS-infiltrating CD4+ effector T cells from mixed congenic co-transfer recipient mice revealed an important, cell-intrinsic, function of GATA3 in regulating the expression of Egr2, Bhlhe40, and Csf2. Thus, our data highlights a novel role for GATA3 in promoting and maintaining the pathogenicity of T-bet-expressing Th17 cells in EAE, via putative regulation of Egr2, Bhlhe40, and GM-CSF expression.

Crosstalk between ILC2s and Th2 cells varies among mouse models

Type 2 T helper (Th2) cells and group 2 innate lymphoid cells (ILC2s) provide protection against helminth infection and are involved in allergic responses. However, their relative importance and crosstalk during type 2 immune responses are still controversial. By generating and utilizing mouse strains that are deficient in either ILC2s or Th2 cells, we report that interleukin (IL)-33-mediated ILC2 activation promotes the Th2 cell response to papain; however, the Th2 cell response to ovalbumin (OVA)/alum immunization is thymic stromal lymphopoietin (TSLP) dependent but independent of ILC2s. During helminth infection, ILC2s and Th2 cells collaborate at different phases of the immune responses. Th2 cells, mainly through IL-4 production, induce the expression of IL-25, IL-33, and TSLP, among which IL-25 and IL-33 redundantly promote ILC2 expansion. Thus, while Th2 cell differentiation can occur independently of ILC2s, activation of ILC2s may promote Th2 responses, and Th2 cells can expand ILC2s by inducing type 2 alarmins.

Gata3 ZsG and Gata3 ZsG-fl: Novel murine Gata3 reporter alleles for identifying and studying Th2 cells and ILC2s in vivo

T helper-2 (Th2) cells and type 2 innate lymphoid cells (ILC2s) play crucial roles during type 2 immune responses; the transcription factor GATA3 is essential for the differentiation and functions of these cell types. It has been demonstrated that GATA3 is critical for maintaining Th2 and ILC2 phenotype in vitro; GATA3 not only positively regulates type 2 lymphocyte-associated genes, it also negatively regulates many genes associated with other lineages. However, such functions cannot be easily verified in vivo because the expression of the markers for identifying Th2 and ILC2s depends on GATA3. Thus, whether Th2 cells and ILC2s disappear after Gata3 deletion or these Gata3-deleted "Th2 cells" or "ILC2s" acquire an alternative lineage fate is unknown. In this study, we generated novel GATA3 reporter mouse strains carrying the Gata3 ZsG or Gata3 ZsG-fl allele. This was achieved by inserting a ZsGreen-T2A cassette at the translation initiation site of either the wild type Gata3 allele or the modified Gata3 allele which carries two loxP sites flanking the exon 4. ZsGreen faithfully reflected the endogenous GATA3 protein expression in Th2 cells and ILC2s both in vitro and in vivo. These reporter mice also allowed us to visualize Th2 cells and ILC2s in vivo. An inducible Gata3 deletion system was created by crossing Gata3 ZsG-fl/fl mice with a tamoxifen-inducible Cre. Continuous expression of ZsGreen even after the Gata3 exon 4 deletion was noted, which allows us to isolate and monitor GATA3-deficient "Th2" cells and "ILC2s" during in vivo immune responses. Our results not only indicated that functional GATA3 is dispensable for regulating its own expression in mature type 2 lymphocytes, but also revealed that GATA3-deficient "ILC2s" might be much more stable in vivo than in vitro. Overall, the generation of these novel GATA3 reporters will provide valuable research tools to the scientific community in investigating type 2 immune responses in vivo.

Myeloid Mayhem: How sleep alters the myeloid compartment and promotes plaque rupture in atherosclerosis

Adequate sleep is vital for overall health; however, today’s fast-paced society often neglects the importance of sleep. Poor sleep quality is tightly correlated with atherosclerosis and increased risk of mortality due to a cardiovascular event. Evidence demonstrates neutrophilia and monocytosis following chronic sleep fragmentation, but their effects on aortic inflammation and atherosclerotic plaque stability are not well understood. We found that chronic sleep fragmentation accelerated atherogenesis and decreased plaque stability in plaques of high fat diet (HFD) fed female apoliportein E-deficient (Apoe−/−) mice. Sleep fragmentation increased populations of pro-inflammatory monocytes and neutrophils in the bone marrow, blood, spleen, and small intestines of HFD fed female Apoe−/− mice. Additionally, sleep fragmentation increased gut permeability and circulating LPS in HFD fed female Apoe−/− mice. We also observed increased percentage of neutrophils in carotid arteries of sleep fragmented Apoe−/− mice. Importantly, these plaques exhibited increased necrotic areas, altered composition of extracellular matrix, and reduced production of stabilizing collagen. Taken together, our data indicates that sleep fragmentation accelerates plaque formation, and destabilizes atherosclerotic plaques by altering the local and systemic immune landscape. Sleep fragmentation contributes to systemic inflammation and likely activates the innate immune response at least partially, through the increase in circulating LPS mediated by inflammation in small intestines.

Recent advances in understanding the Th1/Th2 effector choice

For over 35 years since Mosmann and Coffman proposed the seminal “type 1 T helper (Th1)/type 2 T helper (Th2)” hypothesis in 1986, the immunological community has appreciated that naïve CD4 T cells need to make important decisions upon their activation, namely to differentiate towards a Th1, Th2, Th17 (interleukin-17-producing T helper), follicular T helper (Tfh), or regulatory T cell (Treg) fate to orchestrate a variety of adaptive immune responses. The major molecular underpinnings of the Th1/Th2 effector fate choice had been initially characterized using excellent reductionist in vitro culture systems, through which the transcription factors T-bet and GATA3 were identified as the master regulators for the differentiation of Th1 and Th2 cells, respectively. However, Th1/Th2 cell differentiation and their cellular heterogeneity are usually determined by a combinatorial expression of multiple transcription factors, particularly in vivo, where dendritic cell (DC) and innate lymphoid cell (ILC) subsets can also influence T helper lineage choices. In addition, inflammatory cytokines that are capable of inducing Th17 cell differentiation are also found to be induced during typical Th1- or Th2-related immune responses, resulting in an alternative differentiation pathway, transiting from a Th17 cell phenotype towards Th1 or Th2 cells. In this review, we will discuss the recent advances in the field, focusing on some new players in the transcriptional network, contributions of DCs and ILCs, and alternative differentiation pathways towards understanding the Th1/Th2 effector choice in vivo.

Gata3 regulates the pathogenicity of Tbet-expressing Th17 cells in EAE

Tbet+RORgt+ Th17 cells are thought to be key players in the pathology of experimental autoimmune encephalomyelitis (EAE) and GM-CSF production has been proposed to be one mechanism through which Th17 are encephalitic. However, the mechanisms through which Csf2 expression is regulated are unclear. Based on prior work highlighting a regulatory role for Gata3 in NKp46+ ILC3s, we hypothesized that Gata3 might play an analogous role in Tbet+ Th17 cells during EAE. Profiling Gata3 expression in MOG-immunized mice revealed that Th17 cells dynamically express Gata3 during their differentiation and maintain low levels thereafter. Therefore to determine how Gata3 might affect the pathogenicity of Tbet+ Th17 cells, we utilized tamoxifen inducible Gata3 knockout (Cre-ERT2 Gata3Fl/Fl) mice as donors in a transfer EAE model. In this model, a post-immunization deletion of Gata3 resulted in a failure to generate EAE symptoms due to a five-fold reduction in GM-CSF production, despite a normal Th17 and Tbet+ Th17 cell responses. To assess how Gata3 might affect the expression of Csf2 in a cell-intrinsic manner, we isolated Cd45.1/Cd45.2 and Cre-ERT2 Gata3Fl/Fl CD4+ effector T cells from the CNS of tamoxifen or vehicle treated co-transfer recipient mice for RNAseq. Interestingly, Gata3-deficient CD4+ T cells displayed stark reductions in Bhlhe40, Egr2, and Csf2 expression in a cell-intrinsic manner, which was confirmed in follow-up experiments. Taken together, our data suggests that Gata3 promotes the pathogenicity of Tbet+ Th17 cells in EAE, possibly via regulation of Bhlhe40 and GM-CSF expression.

This research was supported by the Intramural Research Program of NIAID, NIH.

Increased neuroinflammation and atherosclerosis in sleep fragmented mice

There are roughly 70 million Americans who report insufficient sleep due to work responsibilities, sleep apnea, or lifestyle choices. Altered duration and poor sleep quality are associated with an increase in brain inflammation, high rates of cardiovascular disease and other inflammatory diseases in humans. It is known that psychological stress is associated with increased atherogenesis, it is also known that sleep fragmentation (SF) can exacerbate and be induced by SF. However, the exact relationship between SF, neuroinflammation, and atherogenesis is not well known. We found that chronic SF led to increased plaque formation in the aortas HFD fed Apoe−/− mice. SF also resulted in alterations in the immune composition of the bone marrow (BM), blood, aortas, and lymph nodes in the HFD fed Apoe−/− mice. Importantly we detected an increased content of myeloid cells in the blood of SF and HFD fed female Apoe−/− mice. There was an increased percentage of CD68+ macrophages in SF Apoe−/− aortas. Additionally, we detected an increase in CD11b expression and inflammatory markers in the brains of mice that were sleep fragmented when compared to control mice. Our data suggest that SF induces elevated myelopoeisis resulting in monocytosis, neutrophilia, and the altered immune composition of the aortas of atherosclerosis-prone mice, resulting in accelerated atherosclerotic plaque burden.

Characterization of Islet Leukocyte Populations in Human and Murine Islets by Flow Cytometry

An increasing body of evidence indicates that a local islet immune response is not only limited to type 1 diabetes, but also is associated with islet dysfunction in type 2 diabetes. Recently, the presence of pancreatic CD68⁺ macrophages within islet tissues was demonstrated by RT-PCR and immunohistochemical methods. However, the precise profile and activation status of intraislet leukocytes, which are present in both murine and human islets, are poorly defined. Here, we describe a detailed flow cytometry protocol designed to analyze both human and murine islets for intraislet leukocytes and leukocyte subsets. This approach permits the simultaneous identification of multiple intraislet leukocyte subsets, as well as their activation statuses. The use of flow cytometry-based approaches will advance the field of islet biology and help to identify unique changes in the immune cell composition that accompanies pathological islet inflammation and dysfunction in type 2 diabetes.

Gata3 plays a supportive role for the development of Tbet-expressing Th17 cells in EAE

IFNg+IL-17A+(or Tbet+RORgt+) Th17 cells are known to be key players in the pathology of experimental autoimmune encephalomyelitis (EAE), however the dynamics and overall stability of Tbet+ Th17 cells is less clear. Recent data from our lab (Zhong, C. et.al. 2016) has demonstrated that Gata3 plays a role in deciding the balance between Tbet and RORgt expression in gut NKp46+ ILC3 cells. Here, we hypothesized that Gata3 might be expressed by Th17 cell subsets during EAE, and that Gata3 expression would affect the generation or functionality of Tbet-expressing Th17 cells. Surprisingly, we found that all differentiating polyclonal and 2D2 transgenic Th17 cells upregulate Gata3 and subsequently maintain low levels of Gata3 thereafter, both in vitro and in vivo. Additionally, the re-stimulation or re-polarization of Th17 cells does not further affect Gata3 expression, reaffirming that Gata3 is induced during de novo Th17 polarization. To examine how the loss of Gata3 might affect the generation of Th17 or Tbet+ Th17 cells in EAE, we utilized complimentary Gata3 conditional knockout models. In a tamoxifen-inducible Gata3 knockout system, Tamoxifen treated CreERT2 Gata3Fl/Flmice (d6 P.I.) were resistant to EAE, and failed to mount a robust Tbet+Th17 response in comparison to vehicle controls. Similarly, Tbet-dependent Gata3 knockout Tbx21CreGata3Fl/Flmice failed to mount a robust Tbet+ Th17 response in the dLN or CNS, and were resistant to EAE symptoms in active and passive EAE models. Together, these data suggest that while all Th17 cells induce and maintain Gata3 expression, Tbet+ Th17 cells require Gata3 for their generation and survival in EAE.

This research was supported by the Intramural Research Program of NIAID, NIH.

Plasticity and functionality of Th17 subsets in EAE

Several studies have suggested that IFNγ+IL-17A+ (or Tbet+RORγt+) Th17-like cells may be the key players in Experimental Autoimmune Encephalomyelitis (EAE). However, direct evidence demonstrating the importance and functionality of Tbet+RORγt+cells is lacking. Therefore, we examined the generation and stability of Th17 subsets during EAE, and assessed the contributions of RORγt and T-bet to the functionality of these cells. Using Tbx21ZsGreenRorcE2CrimsonFoxp3Rfp/y reporter mice, we were able to isolate T-bet and RORγt single and dual expressors after EAE induction. In a passive EAE model, we observed that donor RORγt-expressing Th17 cells elicited EAE passively and either maintained their phenotype, expressed T-bet, or became non-canonical Th1 cells (expressing T-bet only) in the recipients’ CNS. By contrast, T-bet and RORγt dual expressors largely assumed a non-cannonical Th1 cell fate; while donor Tbet+RORγt− cells maintained their phenotype and failed to elicit EAE. To assess if sustained RORγt expression in Tbet+ Th17 cells is required for the pathogenesis of EAE, we immunized Tbx21CreRorcFl/Fl and RorcFl/Fl mice. Interestingly, Tbet-dependent Rorc knockout mice did not develop EAE symptoms, and Tbet+ Th17 cells were absent in the CNS and dLNs. To examine the importance of RORgt downregulation by T-bet, we generated T-bet and Runx motif mutations within the Rorc promoter via Crispr/Cas9. RorcΔTbet/Runx mice similarly failed to develop EAE symptoms. Together these data suggest that Th17 cell subsets are functionally plastic and that the balance between T-bet and RORγt is required for the functionality of Th17/Th1 cells in EAE.

IL-12 induced STAT4 activation plays a role in pro-inflammatory neutrophil functions

Signal transducer and activator of transcription 4 (STAT4) becomes activated via Jak/Tyk kinases in response to IL-12 and other cytokines, leading to expression of genes involved in pro-inflammatory pathways. STAT4 has been well characterized in T lymphocytes and NK cells, yet less is known of its potential role in neutrophils. Neutrophils have recently been shown to play a contributing role in atherogenesis. Our published data demonstrate that global deficiency of STAT4 results in decreased atherogenesis in atherosclerotic ApoE−/− mice. However, the cell specific role of STAT4 in atherosclerosis is unknown. Western blot analysis revealed STAT4 expression and IL-12 induced phospho-STAT4 in isolated neutrophils with no distinguishable difference between blood and bone marrow neutrophils. IL-12 dependent activation of wild-type (WT) neutrophils induced an increase in reactive oxygen species (ROS) production when compared to non-stimulated WT neutrophils in both blood and bone marrow. Similarly, IL-12 stimulated WT neutrophils showed an increase in neutrophil extracellular trap (NET) elastase activity versus unstimulated controls. IL-12 stimulated neutrophils from Stat4−/− mice displayed no changes in NET elastase activity when compared to non-stimulated STAT4 deficient neutrophils suggesting STAT4-dependent NETosis. Furthermore, IL-12 stimulated Stat4−/− neutrophils showed decreases in both ROS production and NET elastase activity when compared to IL-12 stimulated WT neutrophils. Our data suggest a novel pro-inflammatory, IL-12 dependent role of STAT4 in neutrophils. Inhibition of these processes by targeting the IL-12/STAT4 pathway may serve as a possible therapeutic approach to treating atherosclerosis.

Chronic Sleep Fragmentation Plays A Pro-Atherogenic Role In Atherogenesis

Atherosclerosis is a chronic, inflammatory disease characterized by the hardening and narrowing of the small and medium sized arteries caused by the accumulation of fatty plaque lesions. In the USA, approximately 30% of the population reports insufficient sleep, and nearly 70 million people have a diagnosed sleep disorder. Chronic sleep fragmentation (SF) has been shown to have a connection with the development of many common diseases such as, type 2 diabetes, obesity, and cardiovascular disease; however the exact relationship between SF and the progression of atherosclerosis is unknown. Importantly, SF is related to stress conditions, but also has additional unique components that may affect atherogenesis. To examine the effects of SF on atherosclerosis, Apoe−/− mice were placed on a high fat diet (HFD) and sleep was fragmented using a motorized slow moving mechanical sweeper every 2 minutes during the light period each day. After 9 weeks on HFD and SF we found that chronic SF led to increases in plaque formation in HFD fed Apoe−/− mice. The development of atherosclerotic lesions is characterized by the recruitment of leukocytes and myeloid cells into atherosclerotic arteries. To determine if SF alters the immune composition within atherosclerotic aortas, we examined aortic infiltrating leukocyte subpopulations by FACS. We found that the relative proportion of CD45+ cells from SF Apoe−/− aortas was elevated in comparison with control Apoe−/− aortas. We also detected an increased percentage of CD11b+CD115+ macrophages in SF Apoe−/− aortas. Together our data suggests that chronic SF is pro-atherogenic, alters the immune composition of atherosclerosis-prone aortas and facilitates the accumulation of macrophages within the aortic wall.

Dampening the B Cell Response, a modified lipid story

Atherosclerosis is a multifaceted chronic inflammatory disease characterized by the accumulation of modified low density lipoproteins (mLDL) and immune cells in the aortic wall leading to vascular dysfunction. Uptake of mLDL by macrophages (MF) and the formation of foam cells are key events in the induction of atherosclerosis. Our data shows that B cells can also uptake acetylated and oxidized LDL (acLDL and oxLDL, respectively), but the functional consequences of this uptake are currently not well-understood. The transcriptional profiles of sorted B cells that took up acLDL in vivo by RNAseq suggests that acLDL+ B cells assume a role distinct from MF, and reduces activation. Upon mLDL uptake, B cells dampen activating signaling molecule such as SYK, ERK, and BTK, but upregulate inhibitory signaling molecules such as phospho-Lyn (Tyr507). Importantly, the uptake of mLDL affects the ability of B cells to be activated both in vivo and in vitro. mLDL+ B cells mobilize less intracellular calcium in response to B cell receptor cross-linking. Additionally, after mLDL uptake, B cells are less efficient in response to TI-2 antigen DNP-Ficoll and B cells produce significantly lower levels of anti DNP-IgM Abs after the immunization. Upon several TLR stimulations B cells that took up acLDL also produce significantly less proinflammatory cytokines (IFN-g, IL-6). Together the results suggest that mLDL uptake by B cells results in an upregulation of threshold for B cell activation in pro-inflammatory atherosclerosis-prone conditions. Thus, the uptake of mLDL by B cells may play an unexpected protective role in atherosclerosis.

Atherosclerosis-Driven Treg Plasticity Results in Formation of a Dysfunctional Subset of Plastic IFNγ+ Th1/Tregs

RATIONALE

Forkhead box P3⁺ T regulatory cells (Tregs) are key players in maintaining immune homeostasis. Evidence suggests that Tregs respond to environmental cues to permit or suppress inflammation. In atherosclerosis, Th1-driven inflammation affects Treg homeostasis, but the mechanisms governing this phenomenon are unclear.

OBJECTIVE

Here, we address whether atherosclerosis impacts Treg plasticity and functionality in Apoe^-/- mice, and what effect Treg plasticity might have on the pathology of atherosclerosis.

METHODS AND RESULTS

We demonstrate that atherosclerosis promotes Treg plasticity, resulting in the reduction of CXCR3⁺ Tregs and the accumulation of an intermediate Th1-like interferon (IFN)-γ⁺CCR5⁺ Treg subset (Th1/Tregs) within the aorta. Importantly, Th1/Tregs arise in atherosclerosis from bona fide Tregs, rather than from T-effector cells. We show that Th1/Tregs recovered from atherosclerotic mice are dysfunctional in suppression assays. Using an adoptive transfer system and plasticity-prone Mir146a^-/- Tregs, we demonstrate that elevated IFNγ⁺ Mir146a^-/- Th1/Tregs are unable to adequately reduce atherosclerosis, arterial Th1, or macrophage content within Apoe^-/- mice, in comparison to Mir146a^+/+ Tregs. Finally, via single-cell RNA-sequencing and real-time -polymerase chain reaction, we show that Th1/Tregs possess a unique transcriptional phenotype characterized by coexpression of Treg and Th1 lineage genes and a downregulation of Treg-related genes, including Ikzf2, Ikzf4, Tigit, Lilrb4, and Il10. In addition, an ingenuity pathway analysis further implicates IFNγ, IFNα, interleukin-2, interleukin-7, CTLA-4 (cytotoxic T-lymphocyte-associated protein 4), T-cell receptor, and Csnk2b-related pathways in regulating Treg plasticity.

CONCLUSIONS

Atherosclerosis drives Treg plasticity, resulting in the accumulation of dysfunctional IFNγ⁺ Th1/Tregs that may permit further arterial inflammation and atherogenesis.

Smooth Muscle Cell-Derived Interleukin-17C Plays an Atherogenic Role via the Recruitment of Proinflammatory Interleukin-17A+ T Cells to the Aorta

OBJECTIVE

Atherosclerosis is characterized by frequent communication between infiltrating leukocytes and vascular cells, through chemokine and cytokine networks. Interleukin-17C (IL-17C) is detectable within atherosclerotic lesions; however, the potential involvement of this cytokine has not been examined. Thus, we sought to investigate the role of IL-17C in atherosclerosis.

APPROACH AND RESULTS

The expression of IL-17 cytokines was profiled within aortas of apolipoprotein E double knockout (Apoe(-/-)) mice, and Il17c expression was elevated. Flow cytometry experiments revealed a major population of aortic IL-17C-producing smooth muscle cells. Next, we generated Il17c(-/-)Apoe(-/-) mice and demonstrated that atherosclerotic lesion and collagen content was diminished within Western diet-fed Il17c(-/-)Apoe(-/-) aortas and aortic roots in comparison to Apoe(-/-) controls. Smooth muscle cells and fibroblasts were mainly responsible for the reduced Col1A1 expression in the aorta of Il17c(-/-)Apoe(-/-) mice. Importantly, IL-17C-treated Apoe(-/-) aortas showed upregulated Col1A1 expression ex vivo. Il17c(-/-)Apoe(-/-) mice displayed a proportional reduction in aortic macrophages, neutrophils, T cells, T helper 1 cells, and T regulatory cells, without corresponding changes in the peripheral immune composition. Examination of aortic IL-17A(+) T-cell receptor γδ T cells and Th17 cells demonstrated a stark reduction in the percentage and number of these subsets within Il17c(-/-)Apoe(-/-) versus Apoe(-/-) mice. Explanted 12-week Western diet-fed Apoe(-/-) aortas treated with IL-17C resulted in the induction of multiple vascular chemokines and cytokines. Th17 cells demonstrated attenuated migration toward supernatants from cultures of Il17c(-/-)Apoe(-/-) smooth muscle cells, and short-term homing experiments revealed diminished recruitment of Th17 cells to the aorta of Il17c(-/-)Apoe(-/-) recipients.

CONCLUSIONS

Smooth muscle cell-derived IL-17C plays a proatherogenic role by supporting the recruitment of Th17 cells to atherosclerotic lesions.

Abstract 447: Atherosclerosis-driven Treg Plasticity Results in the Formation of a Dysfunctional Subset of Plastic IFNg + Th1/Tregs

Foxp3 + T regulatory cells (Tregs) are key players in maintaining immune homeostasis. Emerging evidence suggests that Tregs respond to environmental cues to permit or suppress inflammation. In atherosclerosis, Th1-driven inflammation affects Treg homeostasis, but the mechanisms governing this phenomenon are unclear. Here, we addressed whether atherosclerosis impacts Treg plasticity or functionality in Apoe -/- mice and what effect Treg plasticity might have on the pathology of atherosclerosis. We demonstrate that atherosclerosis promotes Treg plasticity, resulting in the reduction of CXCR3 + Tregs, and the accumulation of an intermediate Th1-like IFNγ + CCR5 + Treg subset (Th1/Tregs) within the arterial wall. Using Foxp3 Gfp/Gfp and Foxp3 Yfp-cre/Yfp-cre Rosa tdTomato/tdTomato lineage tracing mice, we demonstrate that Th1/Tregs arise in atherosclerosis from bona fide Tregs, rather than T effector cells. Th1/Tregs recovered from atherosclerotic mice are dysfunctional in suppression assays. Importantly, using Mir146a -/- mice, we demonstrate that plasticity-prone Mir146 -/- Tregs fail to reduce atherosclerosis, arterial Th1, or macrophage content in Apoe -/- recipients. Lastly, we utilized single cell RNA-sequencing to gain whole transcriptome information on Th1/Tregs, Treg, and Th1 cells. Th1/Tregs yielded a unique transcriptional phenotype characterized by co-expression of Treg and Th1 lineage genes, and down-regulation of Treg-related genes, including Ikzf2 , Ikzf4, Tigit, and Lilrb4 . Additionally, an ingenuity pathway analysis further implicates IFNγ, IFNα, IL-2, IL-7, CTLA4, T cell receptor, and Csnk2b-related pathways in regulating Treg plasticity. In conclusion, atherosclerosis drives Treg plasticity, resulting in the accumulation of dysfunctional IFNγ + Th1/Tregs that permit further arterial inflammation and atherogenesis.

Abstract 584: Smooth Muscle Cell-derived IL-17C Plays an Atherogenic Role via the Recruitment of Pro-inflammatory IL-17A + T Cells to the Aorta

Atherosclerosis is characterized by frequent communication between infiltrating leukocytes and vascular cells, through chemokine and cytokine networks. IL-17 cytokine family members, including IL-17C, are detectable within atherosclerotic plaques, however the potential involvement of these cytokines have not been examined. Thus we sought to investigate the role of IL-17C in atherosclerosis. The expression of IL-17 cytokines was profiled within atherosclerotic Apoe -/- aortas and Il17c expression was elevated. Flow cytometry experiments revealed a major population of aortic IL-17C-producing smooth muscle cells. To determine the role of IL-17C in atherosclerosis, we generated Il17c -/- Apoe -/- mice and compared atherosclerotic lesions between western diet-fed Apoe -/- and Il17c -/- Apoe -/- mice. Atherosclerotic lesion and collagen content was diminished within WD-fed Il17c -/- Apoe -/- aortas and aortic roots in comparison to Apoe -/- controls, and IL-17C treated Apoe -/- aortas up-regulated Col1A1 expression ex vivo . Flow cytometric analysis of Il17c -/- Apoe -/- aortas revealed a proportional reduction in aortic leukocytes, macrophages, neutrophils, T cells, Th1, and T regulatory cells, without corresponding changes in the peripheral immune composition. Examination of aortic IL-17A + TCRγδ T cells and Th17 cells demonstrated a stark reduction in the percentage and number of these subsets within Il17c -/- Apoe -/- mice versus Apoe -/- controls. Explanted 12 week WD Apoe -/- aortas treated with IL-17C resulted in the induction of multiple vascular chemokines and cytokines, and short-term homing experiments revealed diminished recruitment of Th17 cells to the aorta of Il17c -/- Apoe -/- recipients. Smooth muscle cell-derived IL-17C plays a pro-atherogenic role by supporting the recruitment of Th17 cells to atherosclerotic lesions.

How is delayed ejaculation defined and treated in North America?

Delayed ejaculation (DE) is an uncommon disorder that is difficult to treat because it is poorly understood. The aim was to evaluate the current opinion and clinical management of DE by practitioners in sexual medicine. Members of the Sexual Medicine Society of North America (SMSNA) were invited by email to participate in a web-based survey. The questionnaire consisted of eight questions pertaining to DE. Questions addressed patient volume, qualification of patient bother, ranking of etiologies, perceived success, treatments used, quantification of symptom resolution, and broad characterization of practitioner type. A total of 94 respondents completed the survey with 73% of those being urologists. Fifty-nine percent of the respondents saw ≤ 2 patients a month with DE and 89% of practitioners felt that DE was moderately or severely bothersome to the patients. Etiology was felt to be from medications and psychological factors primarily. Despite treatment modality, 'seldom' success was obtained for 49% of the time and 'never' for 11%. Carbergoline was the most common selected medication for DE. Academic and private urologists reported 'never' or 'seldom' success with sexual counseling compared to other practitioners, respectively (p = 0.008 and p = 0.001). Respondents who saw ≤ 2 patients per month often reported normalization of hypogonadism 'never' or 'seldom' corrected DE (p = 0.047). Delayed ejaculation is still a poorly understood disorder with inconsistent practice patterns seen among members of the SMSNA. A better understanding of this vexing disorder is needed with efforts placed on research and practitioner education.

CXCR6 regulates the recruitment of pro-inflammatory IL-17A-producing T cells into atherosclerotic aortas

The adaptive immune response is involved in the development and progression of atherosclerosis and IL-17A(+) cells play a role in this disease. Although elevated number of CD4(+) IL-17A(+) (Th17) and IL-17A(+)TCRγδ(+) T cells are found within murine atherosclerotic aortas and human plaques, the mechanisms governing IL-17A(+) T-cell migration to atherosclerotic lesions are unclear. The chemokine receptor CXCR6 is expressed on several T-cell subsets and plays a pro-atherogenic role in atherosclerosis. Here, we used CXCR6-deficient (Cxcr6 (GFP/GFP) ) apolipoprotein E-deficient (Apoe (-/-) ) mice to investigate the involvement of CXCR6 in the recruitment IL-17A(+) T cells to atherosclerotic aortas. Flow cytometric analyses revealed reductions in Th17 and IL-17A(+)TCRγδ(+) T cells within aged Cxcr6 (GFP/GFP) Apoe (-/-) aortas, in comparison with age-matched Cxcr6 (GFP/+) Apoe (-/-) aortas. Although CXCR6-sufficient IL-17A(+) T cells efficiently migrated toward CXCL16, the migration of CXCR6-deficient IL-17A(+) T cells was abolished in transwell assays. Importantly, the recruitment of Cxcr6 (GFP/GFP) Apoe (-/-) IL-17A(+) T cells into the aortas of Apoe (-/-) recipients was markedly reduced in short-term adoptive transfer experiments. Altogether these results demonstrate an important role of CXCR6 in the regulation of pathological Th17 and IL-17A(+)TCRγδ(+) T-cell recruitment into atherosclerotic lesions.

Abstract 552: IL-17C-Producing Aortic Smooth Muscle Cells Play a Pro-Atherogenic Role Via the Recruitment of Inflammatory IL-17A+ T Cells

Atherosclerosis is characterized by frequent communication between infiltrating leukocytes and vascular cells, through chemokine and cytokine networks. Various IL-17 cytokine family members are detected within atherosclerotic plaques; however the involvement of IL-17B-IL-17E has not been thoroughly examined. Aortic IL-17 cytokines were initially profiled and Il17a, Il17f, and Il17c mRNA expression was found to be elevated in Apoe-/- aortas in comparison to C57Bl6 controls. To determine the cellular sources of aortic IL-17C, aortic IL-17C-producing cells were phenotyped by flow cytometry. Surprisingly, these experiments revealed a major population of IL-17C-producing smooth muscle cells within Apoe-/- versus C57Bl6 aortas. To determine the role of IL-17C in atherosclerosis, we generated Il17c-/-Apoe-/- mice and compared 12 week western diet-fed Apoe-/- and Il17c-/-Apoe-/- mice. Atherosclerotic lesions were reduced by 42±2.6% in WD-fed Il17c-/-Apoe-/- aortas in comparison to Apoe-/- controls. Flow cytometric analyses of Il17c-/-Apoe-/- mice revealed a reduction in the number of aortic leukocytes, macrophages, neutrophils, and T cells, which corresponded with smaller atherosclerotic lesions (40±5%). However, the percentage and number of aortic IL-17A+ TCRγδ T cells and Th17 cells were disproportionately reduced within Il17c-/-Apoe-/- aortas (70±5%). We hypothesized that IL-17C might support the recruitment of Th17 cells to the aorta. To study comparative Th17 migration, Apoe-/- T cells were transferred to western diet-fed Il17c-/-Apoe-/- and Apoe-/- recipients and examined for Th1 and Th17 migration 48 hours post transfer. We found diminished accumulation of Th17, but not Th1 T cells, in the aortas of Il17c-/-Apoe-/- versus Apoe-/- recipients. Thus smooth muscle cell-derived IL-17C plays a pro-atherogenic role by supporting the recruitment of Th17 cells to atherosclerotic lesions.

Abstract 350: The Pro-atherosclerotic Milieu Converts a Sub-population of Murine Peripheral T Regulatory Cells to a Non-suppressive Th1-like Foxp3+IFNγ+ Phenotype

CD4+ T cell subsets play diverse roles in inflammation but may also display limited plasticity. The existence of a population of Foxp3+ T regulatory (Treg) cells that co-expresses Interferon-γ (IFNγ) has been demonstrated in several models of inflammation. In atherosclerosis, circulating Treg content inversely corresponds with atherogenesis, suggesting that inflammation might affect peripheral Treg (pTregs) maintenance. Thus, we sought to examine the fate of pTregs within atherosclerotic Apolipoprotein E-deficient (Apoe-/-) mice. Foxp3+IFNγ+ T cells were elevated within the aorta, spleen, and peripheral lymph nodes (PLNs) of atherosclerotic Apoe-/- versus C57BL/6 mice. Further phenotyping of Foxp3+IFNγ+ T cells revealed variable expression of Treg and Th1 markers, including low CTLA4, GITR, CD25 expression, equivalent PD1, CD73, FR4, expression and elevated Tbet, CD119, CXCR3, and CCR5 expression. To determine whether Foxp3+IFNγ+ T cells arise from de novo differentiation or peripheral conversion, we performed fate tracking experiments with co-adoptively transferred naïve T cells and pTregs, or lineage tracing Foxp3yfp-cre+ R26RtdTomato+ pTregs, to aged Apoe-/- mice. Naïve T cells failed to generate Foxp3+IFNγ+ T cells. In contrast, adoptively transferred Tregs maintained Foxp3 expression (50-60%) or adopted a Foxp3+IFNγ+ T phenotype (40-50%) within the spleen, peri-aortic lymph nodes, and aorta. To test the functionality of IFNγ+ Tregs, we isolated IFNγ+ pTregs, IFNγ- pTregs, and Foxp3GFP+ Tregs for T cell suppression assays. While IFNγ- pTregs and Foxp3GFP+ pTregs were equivalently suppressive, IFNγ+ pTregs failed to adequately suppress T cell proliferation. Together these results demonstrate that atherogenic inflammation affects the maintenance of pTregs, resulting in the generation of a subset of dysfunctional Foxp3+IFNγ+ T cells.

The dynamic lives of macrophage and dendritic cell subsets in atherosclerosis

Atherosclerosis, the major pathological process through which arterial plaques are formed, is a dynamic chronic inflammatory disease of large- and medium-sized arteries in which the vasculature, lipid metabolism, and the immune system all play integral roles. Both the innate and adaptive immune systems are involved in the development and progression of atherosclerosis but myeloid cells represent the major component of the burgeoning atherosclerotic plaque. Various myeloid cells, including monocytes, macrophages (MΦs), and dendritic cells (DCs) can be found within the healthy and atherosclerotic arterial wall, where they can contribute to or regulate inflammation. However, the precise behaviors and functions of these cells in situ are still active areas of investigation that continue to yield exciting and surprising new data. Here, we review recent progress in understanding of the complex biology of MΦs and DCs, focusing particularly on the dynamic regulation of these subsets in the arterial wall and novel, emerging functions of these cells during atherogenesis.

Association of proinflammatory cytokines and islet resident leucocytes with islet dysfunction in type 2 diabetes

AIMS/HYPOTHESIS

Chronic inflammation in type 2 diabetes is proposed to affect islets as well as insulin target organs. However, the nature of islet inflammation and its effects on islet function in type 2 diabetes remain unclear. Moreover, the immune cell profiles of human islets in healthy and type 2 diabetic conditions are undefined. We aimed to investigate the correlation between proinflammatory cytokine expression, islet leucocyte composition and insulin secretion in type 2 diabetic human islets.

METHODS

Human islets from organ donors with or without type 2 diabetes were studied. First and second phases of glucose-stimulated insulin secretion were determined by perifusion. The expression of inflammatory markers was obtained by quantitative PCR. Immune cells within human islets were analysed by FACS.

RESULTS

Type 2 diabetic islets, especially those without first-phase insulin secretion, displayed higher CCL2 and TNFa expression than healthy islets. CD45(+) leucocytes were elevated in type 2 diabetic islets, to a greater extent in moderately functional type 2 diabetic islets compared with poorly functional ones, and corresponded with elevated ALOX12 but not with CCL2 or TNFa expression. T and B lymphocytes and CD11c(+) cells were detectable within both non-diabetic and type 2 diabetic islet leucocytes. Importantly, the proportion of B cells was significantly elevated within type 2 diabetic islets.

CONCLUSIONS/INTERPRETATION

Elevated total islet leucocyte content and proinflammatory mediators correlated with islet dysfunction, suggesting that heterogeneous insulitis occurs during the development of islet dysfunction in type 2 diabetes. In addition, the altered B cell content highlights a potential role for the adaptive immune response in islet dysfunction.

Interaction between cytokines and inflammatory cells in islet dysfunction, insulin resistance and vascular disease

Inflammation is an established pathogenic player in insulin resistance, islet demise and atherosclerosis. The complex interactions between cytokines, immune cells and affected tissues result in sustained inflammation in diabetes and atherosclerosis. 12- and 15-lipoxygenase (LO), such as 12/15-LO, produces a variety of metabolites through peroxidation of fatty acids and potentially contributes to the complex molecular crosstalk at the site of inflammation. 12- and 15-LO pathways are frequently activated in tissues affected by diabetes and atherosclerosis including adipose tissue (AT), islets and the vasculature. Moreover, mice with whole body and tissue-specific knockout of 12/15-LO are protected against insulin resistance, hyperglycaemia and atherosclerosis supporting functional contribution of 12- and 15-LO pathways in diabetes and atherosclerosis. Recently, it has emerged that there is a temporal regulation of the particular isoforms of 12- and 15-LO in human AT and islets during the development of type 1 and type 2 diabetes and obesity. Analyses of tissues affected by diabetes and atherosclerosis also implied the roles of interleukin (IL)-12 and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-1 (NOX-1) in islets and IL-17A in atherosclerosis. Future studies should aim to test the efficacy of inhibitions of these mediators for treatment of diabetes and atherosclerosis.

Abstract 186: Aortic IL-17C Producing Cells in Atherosclerosis

The progression of atherosclerosis from fatty acid streaks to complex lesions involves regular communication between hematopoetic cells within the arterial wall and vascular cells via cytokine and chemokine networks. Recent evidence has demonstrated the presence of Interleukin-17A (IL-17A)-producing T cells within atherosclerotic Apolipoprotein E-deficient (Apoe-/-) aortas. IL-17A is a member of the IL-17 cytokine family, which consists of six related isoforms (IL-17A-IL-17F). While the functions of IL-17A, IL-17E, and IL-17F are the subject of ongoing studies, the roles and producers of IL-17B and IL-17C remain elusive. Recent studies have demonstrated a pro-inflammatory role for epithelial cell and keratinocyte-derived IL-17C in the context of experimental colitis, and psoriasis. In the present study, we sought to examine the expression of IL-17C within the aortas of atherosclerotic Apoe-/- and Il17a-/-Apoe-/- mice. We detected Il17c mRNA within the aortas of both 12-week western diet-fed Apoe-/- and Il17a-/-Apoe-/- mice. To further identify and characterize the cellular sources of aortic IL-17C, we examined aortic leukocytes and vascular cells by flow cytometry. We identified several major cellular producers of IL-17C in vivo, including a major population of smooth muscle cells (5±0.8% of Apoe-/- CD45-αSMA+ SMCs) and a population of CD45-αSMA- cells (5.8±0.8% of Apoe-/- CD45-αSMA- cells). Interestingly, the percentage of aortic IL-17C producing cells was elevated within 12 week western diet-fed Il17a-/-Apoe-/- mice in comparison to Apoe-/- littermates (6.16±0.24% of the Il17a-/-Apoe-/- aorta vs 3.6±0.1% of the Apoe-/- aorta), suggesting an inverse relationship between T cell derived-IL-17A and vascular-IL-17C. To examine the effects of IL-17C and the possibility of synergy between TNFα and IL-17C on aortic chemokine and cytokine production, we explanted and treated whole aortas with IL-17C or IL-17C and TNFα in vitro. IL-17C with and without TNFα broadly supported the expression of Ccl2, Ccl7, Cxcl1, Cxcl2, Cxcl5, and Il6 in explanted WD Apoe-/- aortas. Together, these results suggest that vascular smooth muscle cell-derived IL-17C may play a pro-inflammatory role in atherosclerosis via the production of chemokines and cytokines.

Abstract 385: Conversion of Established Murine Inducible T Regulatory Cells to Foxp3+IFN?+ T Cells in Atherosclerosis Occurs in an IL-12 Dependent Manner

In inflammation, T cell subsets are known to play diverse roles and recent evidence suggests that T helper cells display limited plasticity under specific stimuli. Evidence indicates that a decrease in the number of circulating Tregs corresponds with atherogenesis, and the existence of a population of Foxp3+ T regulatory cells that co-expresses inflammatory cytokines such as Interleukin-17A (IL-17A) and Interferon γ (IFNγ) has been demonstrated in models of inflammation. However, the cellular precursors and mechanisms underlying the generation of Foxp3+IL-17A+ and Foxp3+IFNγ+ T cells are unclear. Thus, we sought to study the fate of T regulatory cells during atherogenesis within 12 week western diet (WD)-fed Apolipoprotein E-deficient (Apoe-/-) mice. Apoe-/- mice have a population of Foxp3+IFNγ+ T regulatory cells within the aorta, spleen, peripheral lymph nodes (PLNs), peri-aortic LNs (PALNs), and mesenteric LNs (MLNs). To determine whether Foxp3+IFNγ+ Tregs arise from de novo differentiating naïve T cells or established Tregs, we performed a series of fate tracking experiments with co-adoptively transferred naïve T cells and inducible T regs in Apoe-/- mice. Both adoptively transferred T regs and naïve T cells were present in the blood and emigrated to the aorta, spleen, PLNs, MLNs, and PALNs of Apoe-/- mice. While naïve T cells were present in the tissues examined, they failed to appreciably differentiate to effector T cell fates. In contrast, half of the adoptively transferred Treg cells lost the expression of Foxp3 within all of the tissues examined. The remaining T regs maintained Foxp3 expression (40-45% of transferred Tregs) or adopted a Foxp3+IFNγ+ phenotype (5-10%). To assess how established T reg cells may convert to Foxp3+IFNγ+ T cells, in vitro differentiated iTregs were maintained in Treg conditions with or without IL-12 and assessed by flow cytometry. iTregs cultured without IL-12 did not become Foxp3+IFNγ+ cells. However in iTreg cultures supplemented with IL-12, 10% of Foxp3+ Tregs co-expressed IFNγ. Together, these results suggest that the pro-inflammatory conditions during atherogenesis affect the maintenance of established Treg cells, resulting in the loss of Foxp3 expression or the generation of Foxp3+IFNγ+ Tregs.

Phenotypic and functional heterogeneity of macrophages and dendritic cell subsets in the healthy and atherosclerosis-prone aorta

Atherosclerosis continues to be the leading cause of cardiovascular disease. Development of atherosclerosis depends on chronic inflammation in the aorta and multiple immune cells are involved in this process. Importantly, resident macrophages and dendritic cells (DCs) are present within the healthy aorta, but the functions of these cells remain poorly characterized. Local inflammation within the aortic wall promotes the recruitment of monocytes and DC precursors to the aorta and micro-environmental factors direct the differentiation of these emigrated cells into multiple subsets of macrophages and DCs. Recent data suggest that several populations of macrophages and DCs can co-exist within the aorta. Although the functions of M1, M2, Mox, and M4 macrophages are well characterized in vitro, there is a limited set of data on the role of these populations in atherogenesis in vivo. Recent studies on the origin and the potential role of aortic DCs provide novel insights into the biology of aortic DC subsets and prospective mechanisms of the immune response in atherosclerosis. This review integrates the results of experiments analyzing heterogeneity of DCs and macrophage subsets in healthy and diseased vessels and briefly discusses the known and potential functions of these cells in atherogenesis.

The IL-17A/IL-17RA axis plays a proatherogenic role via the regulation of aortic myeloid cell recruitment

RATIONALE

Atherosclerosis is a disease of large- and medium-sized arteries that is characterized by chronic vascular inflammation. While the role of Th1, Th2, and T-regulatory subsets in atherogenesis is established, the involvement of IL-17A-producing cells remains unclear.

OBJECTIVE

To investigate the role of the IL-17A/IL-17RA axis in atherosclerosis.

METHODS AND RESULTS

We bred apolipoprotein-E-deficient (Apoe(-/-)) mice with IL-17A-deficient and IL-17 receptor A-deficient mice to generate Il17a(-/-)Apoe(-/-) and Il17ra(-/-)Apoe(-/-) mice. Western diet fed Il17a(-/-)Apoe(-/-) and Il17ra(-/-)Apoe(-/-) mice had smaller atherosclerotic plaques in the aortic arch and aortic roots, but showed little difference in plaque burden in the thoracoabdominal aorta in comparison with Apoe(-/-) controls. Flow cytometric analysis of Il17a(-/-)Apoe(-/-) and Il17ra(-/-)Apoe(-/-) aortas revealed that deficiency of IL-17A/IL-17RA preferentially reduced aortic arch, but not thoracoabdominal aortic T cell, neutrophil, and macrophage content in comparison with Apoe(-/-) aortic segments. In contrast to ubiquitous IL-17RA expression throughout the aorta, IL-17A was preferentially expressed within the aortic arch of WD-fed Apoe(-/-) mice. Deficiency of IL-17A or IL-17RA reduced aortic arch, but not thoracoabdominal aortic TNFα and CXCL2 expression. Aortic vascular IL-17RA supports monocyte adherence to explanted aortas in ex vivo adhesion assays. Short-term homing experiments revealed that the recruitment of adoptively transferred monocytes and neutrophils to the aortas of Il17ra(-/-)Apoe(-/-) mice is impaired in comparison with Apoe(-/-) recipients.

CONCLUSIONS

The IL-17A/IL-17RA axis increases aortic arch inflammation during atherogenesis through the induction of aortic chemokines, and the acceleration of neutrophil and monocyte recruitment to this site.

Flow cytometry analysis of immune cells within murine aortas

Atherosclerosis is a chronic inflammatory process of medium and large size vessels that is characterized by the formation of plaques consisting of foam cells, immune cells, vascular endothelial and smooth muscle cells, platelets, extracellular matrix, and a lipid-rich core with extensive necrosis and fibrosis of surrounding tissues.(1) The innate and adaptive arms of the immune response are involved in the initiation, development and persistence of atherosclerosis.(2, 3) There is a significant body of evidence that different subsets of the immune cells, such as macrophages, dendritic cells, T and B lymphocytes, are present within the aortas of healthy and atherosclerosis-prone mice(4). Additionally, immune cells are found in the surrounding aortic adventitia which suggests an important role of this tissue in atherogenesis.(2) For some time, the quantitative detection of different types of immune cells, their activation status, and the cellular composition within the aortic wall was limited by RT-PCR and immunohistochemical methods for the study of atherosclerosis. Few attempts were made to perform flow cytometry using human aortas, and a number of problems, such as a high autofluorescence, have been reported(5,6). Human atherosclerotic plaques were digested with collagenase 1, and free cells were collected and stained for CD14+/CD11c+ to highlight macrophage-derived foam cells. In this study, a "mock" channel was used to avoid false-positive staining.(6) Necrotic materials accumulating during the digestion process give rise in a large amount of debris that generates a high autofluorescence in aortic samples. To resolve this problem, a panel of negative and positive controls has been proposed, but only double staining could be applied in these samples. We have developed a new flow cytometry-based method(7) to analyze the immune cell composition and characterize the activation, proliferation, differentiation of immune cells in healthy and atherosclerosis-prone aorta. This method allows the investigation of the immune cell composition of the aortic wall and opens possibilities to use a broad spectrum of immunological methods for investigations of immune aspects of this disease.

The use of etched registration markers to make four-terminal electrical contacts to STM-patterned nanostructures

We demonstrate the use of etched registration markers for the alignment of four-terminal ex situ macroscopic contacts created by conventional optical lithography to buried nanoscale Si:P devices, patterned by hydrogen-based scanning tunnelling microscope (STM) lithography. Using SiO(2) as a mask we are able to protect the silicon surface from contamination during marker fabrication and can achieve atomically flat surfaces with atomic-resolution imaging. The registration markers are shown to withstand substrate heating to approximately 1200 degrees C and epitaxial overgrowth of approximately 25 nm Si. Using a scanning electron microscope to position the STM tip with respect to the markers, we can achieve alignment accuracies of approximately 100 nm, which allows us to contact buried Si:P structures. We have applied this technique to fabricate P-doped wires of different widths and measured their I-V characteristics at 4 K, finding ohmic behaviour down to a width of approximately 27 nm.

Local density of states in zero-dimensional semiconductor structures

The local density of states (LDOS) within tetrahedral InAs structures, formed at the surface of InAs/GaAs(111)A, has been characterized using low-temperature scanning tunneling microscopy. The LDOS of the lowest four zero-dimensional (0D) discrete levels have been imaged in structures with a comparable size to the electron wavelength. The LDOS inside the structures is observed to be higher than that of the surrounding area at intervals of the level separation. This feature indicates the singularity of the LDOS close to the 0D resonant levels.

Imaging of Friedel oscillation patterns of two-dimensionally accumulated electrons at epitaxially grown InAs(111) A surfaces

The local density of states (LDOS) at the epitaxially grown InAs surface on a GaAs(111) A substrate were characterized using low-temperature scanning tunneling microscopy. Using dI/dV signal mapping, LDOS standing waves were clearly imaged at point defects and within nanostructures. Measurement of the wavelength as a function of bias voltage showed a nonparabolic dispersion relation for the conduction band. The observed wave features originate from the Friedel oscillations of the two-dimensional electron gas in the semiconductor surface accumulation layer.

The stability and interrelationships of newborn sucking and heart rate

The sucking behavior of 44 newborns was recorded along with heart rate (HR) and respiration. These 3 systems showed stability over a 24-hr period. Sucking parameters varied markedly depending upon whether the infant was sucking for sucrose or under a no-fluid condition. Moreover, HR was strikingly affected by sweetness. The direction of HR change was toward increasing rates when sucking for sweet, even though sucking for sweet substances occurs more slowly than for no fluid.