B cell subset biology in a tumor microenvironment model

The high myeloid to lymphoid ratio of cultured peritoneal cavity (PerC) leukocytes can serve as an in vitro model to study the tumor microenvironment (TME). C57BL/6J PerC T cell responses to TCR ligation (anti-CD3) and mitogen (ConA) are suppressed in these cultures. Likewise, the PerC B cell response to BCR (F[ab’2] anti-IgM) and TLR4 (TLR4L/LPS) ligation are suppressed. T cell suppression can be liberated by neutralizing IFNγ or by blocking iNOS with 1-methyl arginine. The BCR response is recovered by blocking prostaglandin production with indomethacin; the LPS response by neutralizing IL10. To dissect putative receptor-ligand signals in this model, we investigated expression of the inhibitory cell surface marker PDL1/B7H1/CD274 on PerC cells. TCR ligation increased PDL1 expression on macrophages (Mfs), B1, and B2 cells and was reduced by blocking IFNγ. TLR4 ligation increased PDL1 expression on Mfs and both B cell subsets and was reduced by blocking IFNAR1. Interestingly, BCR ligation increased B7H1 and Class II expression on Mfs and B2 cells, but not B-1 cells. Increased B7H1 expression could be reduced by neutralizing IL6, IFNβ, IFNγ, or IFNAR1. TCR ligation led to B1, but not B2, cell division and proliferating B cells increased IL10 production. These findings illustrate that TCR, and surprisingly BCR, ligation can foster immune suppression in macrophage-dense cultures and suggest that regulatory B cells must be considered when designing immunomodulatory cancer therapies.

Loss of humoral immunity in a mouse model of ovarian cancer

Although a low incidence cancer, ovarian carcinoma (OvCa) has a high mortality rate due to late detection. To study the humoral immune response to OvCa we transplant ID8 cells (mouse epithelial carcinoma) into the murine peritoneal cavity (PerC). We found that as the OvCa developed PerC B cells, particularly B-1 B cells, were depleted. To assess the systemic impact of this depletion we assessed humoral immunity. We found a reduction in “natural” IgM and IgG3 production and increased IgA and IgG1. Following immunization, there was loss of the TI-2 response (FITC-dextran, FITC-Ficoll); the TI-1 (FITC-LPS) response was intact until very late stage disease. Since B-1 cells also serve a housekeeping role in apoptotic corpse clearance, we used a FACS assay and a cell-based ELISA to monitor antibodies directed at apoptotic ID8 cells. Mice with OvCa had lower titers of sera that bound apoptotic ID8 cells. Collectively these data validate the systemic loss of B-1 B cells in mice with OvCa. These results could serve to inform strategies designed for early detection of OvCa.

Four-Dimensional Quantum Hall Effect with Ultracold Atoms

We propose a realistic scheme to detect the 4D quantum Hall effect using ultracold atoms. Based on contemporary technology, motion along a synthetic fourth dimension can be accomplished through controlled transitions between internal states of atoms arranged in a 3D optical lattice. From a semiclassical analysis, we identify the linear and nonlinear quantized current responses of our 4D model, relating these to the topology of the Bloch bands. We then propose experimental protocols, based on current or center-of-mass-drift measurements, to extract the topological second Chern number. Our proposal sets the stage for the exploration of novel topological phases in higher dimensions.

EPOR expression by peritoneal macrophages and B1b cells (TUM6P.1010)

Erythropoietin (EPO) is used in the treatment of chemotherapy-related anemia. A higher mortality rate among cancer patients treated with EPO has been documented. Research in this area has focused upon EPOR expression by cancer cells, either cell lines or ex vivo tumor tissue. We find that addition of exogenous EPO suppresses the activation of peritoneal cavity (PerC) T cells. Via FACs analysis of cultured C57BL/6J (wildtype,WT) PerC cells, we detected the EPO receptor (EPOR) on F4/80+, CD11b+ macrophages (Mfs). The specificity of the anti-EPOR pAb was validated by inhibition of staining with soluble EPOR. The percentage of Mfs expressing the EPOR increased with culture duration. EPOR+ Mfs also increased expression of the immunoinhibitory molecule PDL1/B7H1. Interestingly, EPOR expression also appeared on cultured B1b (IgMhi, CD11blo) cells. Although less evident in WT mice assessed ex vivo, EPOR+ PerC Mfs were found in IL10KO mice. Considerably more EPOR+ B1b cells were observed in the inflammatory ascites of mice with the ovarian cancer that develops following injection of the ID8 mouse epithelial carcinoma cell line. We are currently investigating how EPO contributes to T cell suppression in vitro and impacts Mf and B1b cell function and phenotype. Our data support a link between inflammation and EPOR expression by PerC Mfs and B1b cells.

Light-induced gauge fields for ultracold atoms

Gauge fields are central in our modern understanding of physics at all scales. At the highest energy scales known, the microscopic universe is governed by particles interacting with each other through the exchange of gauge bosons. At the largest length scales, our Universe is ruled by gravity, whose gauge structure suggests the existence of a particle-the graviton-that mediates the gravitational force. At the mesoscopic scale, solid-state systems are subjected to gauge fields of different nature: materials can be immersed in external electromagnetic fields, but they can also feature emerging gauge fields in their low-energy description. In this review, we focus on another kind of gauge field: those engineered in systems of ultracold neutral atoms. In these setups, atoms are suitably coupled to laser fields that generate effective gauge potentials in their description. Neutral atoms 'feeling' laser-induced gauge potentials can potentially mimic the behavior of an electron gas subjected to a magnetic field, but also, the interaction of elementary particles with non-Abelian gauge fields. Here, we review different realized and proposed techniques for creating gauge potentials-both Abelian and non-Abelian-in atomic systems and discuss their implication in the context of quantum simulation. While most of these setups concern the realization of background and classical gauge potentials, we conclude with more exotic proposals where these synthetic fields might be made dynamical, in view of simulating interacting gauge theories with cold atoms.

Synthetic gauge fields in synthetic dimensions

We describe a simple technique for generating a cold-atom lattice pierced by a uniform magnetic field. Our method is to extend a one-dimensional optical lattice into the "dimension" provided by the internal atomic degrees of freedom, yielding a synthetic two-dimensional lattice. Suitable laser coupling between these internal states leads to a uniform magnetic flux within the two-dimensional lattice. We show that this setup reproduces the main features of magnetic lattice systems, such as the fractal Hofstadter-butterfly spectrum and the chiral edge states of the associated Chern insulating phases.

Realistic time-reversal invariant topological insulators with neutral atoms

We lay out an experiment to realize time-reversal invariant topological insulators in alkali atomic gases. We introduce an original method to synthesize a gauge field in the near field of an atom chip, which effectively mimics the effects of spin-orbit coupling and produces quantum spin-Hall states. We also propose a feasible scheme to engineer sharp boundaries where the hallmark edge states are localized. Our multiband system has a large parameter space exhibiting a variety of quantum phase transitions between topological and normal insulating phases. Because of their remarkable versatility, cold-atom systems are ideally suited to realize topological states of matter and drive the development of topological quantum computing.

Wilson fermions and axion electrodynamics in optical lattices

We show that ultracold Fermi gases in optical superlattices can be used as quantum simulators of relativistic lattice fermions in 3+1 dimensions. By exploiting laser-assisted tunneling, we find an analogue of the so-called naive Dirac fermions, and thus provide a realization of the fermion doubling problem. Moreover, we show how to implement Wilson fermions, and discuss how their mass can be inverted by tuning the laser intensities. In this regime, our atomic gas corresponds to a phase of matter where Maxwell electrodynamics is replaced by axion electrodynamics: a 3D topological insulator.

Does social status predict adult smoking and obesity? Results from the 2000 Mexican National Health Survey

Socioeconomic status is generally associated with better health, but recent evidence suggests that this 'social gradient' in health is far from universal. This study examines whether social gradients in smoking and obesity in Mexico - a country in the midst of rapid socioeconomic change - conform to or diverge from results for richer countries. Using a nationally representative sample of 39,129 Mexican adults, we calculate the odds of smoking and of being obese by educational attainment and by household wealth. We conclude that socioeconomic determinants of smoking and obesity in Mexico are complex, with some flat gradients and some strong positive or negative gradients. Higher social status (education and assets) is associated with more smoking and less obesity for urban women. Higher status rural women also smoke more, but obesity for these women has a non-linear relationship to education. For urban men, higher asset levels (but not education) are associated with obesity, whereas education is protective of smoking. Higher status rural men with more assets are more likely to smoke and be obese. As household wealth, education and urbanisation continue to increase in Mexico, these patterns suggest potential targets for public health intervention now and in the future.

Non-Abelian optical lattices: anomalous quantum Hall effect and Dirac fermions

We study the properties of an ultracold Fermi gas loaded in an optical square lattice and subjected to an external and classical non-Abelian gauge field. We show that this system can be exploited as an optical analogue of relativistic quantum electrodynamics, offering a remarkable route to access the exotic properties of massless Dirac fermions with cold atoms experiments. In particular, we show that the underlying Minkowski space-time can also be modified, reaching anisotropic regimes where a remarkable anomalous quantum Hall effect and a squeezed Landau vacuum could be observed.

Statistics of the log-det estimator

The log-det estimator is a measure of divergence (evolutionary distance) between sequences of biological characters, DNA or amino acids, for example, and has been shown to be robust to biases in composition that can cause problems for other estimators. We provide a statistical framework to construct high-accuracy confidence intervals for log-det estimates and compare the efficiency of the estimator to that of maximum likelihood using time-reversible Markov models. The log-det estimator is found to have good statistical properties under such general models.

Social inequalities in health disentangling the underlying mechanisms

Differentials in health and longevity by socioeconomic status and by the nature of social relationships have been found in innumerable studies in the social and medical sciences. Three categories of explanations for the observed patterns have been proposed: causal mechanisms through which the social environment affects health status or the risk of dying; selection or reverse causal pathways whereby a person's health status affects their social position; and artifactual mechanisms, such as measurement error. The general consensus among researchers is that the observed disparities in health are driven largely by a complex set of causal processes rather than by selection or by artifactual mechanisms. This paper explores the set of arguments and strategies that researchers have used to arrive at this conclusion. As part of this undertaking, we assess whether inferences regarding the minor contribution of selection to the overall association between social factors and health are justifiable. In addition, we identify current avenues of research that are providing new insights into the causal pathways linking social factors and health.

Complete characterization of the (D2O)2 ground state: high Ka rotation-tunneling levels

We report the observation of extensive a- and c-type rotation-tunneling (RT) spectra of (D2O)2 for Ka = 0-4. These data allow quantification of molecular constants and tunneling splittings for a number of previously unobserved RT states of (D2O)2. The vibrational ground state has thus been characterized to energies as high as those of some of the intermolecular vibrations, and we present the first test of the VRT(ASP-W) potential at these high Ka states.