抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

N G van Kampen 1981 Amsterdam: North-Holland xiv + 419 pp price Dfl 180 This is a book which, at a lower price, could be expected to become an essential part of the library of every physical scientist concerned with problems involving fluctuations and stochastic processes, as well as those who just enjoy a beautifully written book. It provides an extensive graduate-level introduction which is clear, cautious, interesting and readable.

https://iopscience.iop.org/article/10.1088/0031-9112/34/4/040/pdf

Stochastic Processes in Physics and Chemistry

Monocytes and macrophages are critical effectors and regulators of inflammation and the innate immune response, the immediate arm of the immune system. Dendritic cells initiate and regulate the highly pathogen-specific adaptive immune responses and are central to the development of immunologic memory and tolerance. Recent in vivo experimental approaches in the mouse have unveiled new aspects of the developmental and lineage relationships among these cell populations. Despite this, the origin and differentiation cues for many tissue macrophages, monocytes, and dendritic cell subsets in mice, and the corresponding cell populations in humans, remain to be elucidated.

/pdf/development-of-monocytes-macrophages-and-dendritic-cells-5fkinpnur8.pdf

Development of Monocytes, Macrophages, and Dendritic Cells

Hematopoiesis: an evolving paradigm for stem cell biology.

50 Years of Image Analysis

Embryos allocate cells to the three germ layers in a spatially ordered sequence. Human embryonic stem cells (hESCs) can generate the three germ layers in culture; however, differentiation is typically heterogeneous and spatially disordered. We show that geometric confinement is sufficient to trigger self-organized patterning in hESCs. In response to BMP4, colonies reproducibly differentiated to an outer trophectoderm-like ring, an inner ectodermal circle and a ring of mesendoderm expressing primitive-streak markers in between. Fates were defined relative to the boundary with a fixed length scale: small colonies corresponded to the outer layers of larger ones. Inhibitory signals limited the range of BMP4 signaling to the colony edge and induced a gradient of Activin-Nodal signaling that patterned mesendodermal fates. These results demonstrate that the intrinsic tendency of stem cells to make patterns can be harnessed by controlling colony geometries and provide a quantitative assay for studying paracrine signaling in early development.

A method to recapitulate early embryonic spatial patterning in human embryonic stem cells

Multilineage Transcriptional Priming and Determination of Alternate Hematopoietic Cell Fates

Chandra images show symmetric, 8 kpc long, armlike features in the X-ray halo surrounding NGC 4636. The leading edges of these features are sharp and are accompanied by temperature increases of ~30%. These properties suggest that the armlike structures are produced by shocks, driven by symmetric off-center outbursts. We interpret these observations as part of a cycle in which the cooling gas originally fueled a nuclear outburst about 3 × 106 yr ago that led to shocks reheating the cooling gas and thus preventing the accumulation of significant amounts of cooled gas in the galaxy center and temporarily starving the central active galactic nucleus.

/pdf/chandra-observations-of-ngc-4636-an-elliptical-galaxy-in-2o2zqnkro9.pdf

Chandra Observations of NGC 4636-an Elliptical Galaxy in Turmoil

The authors introduce an algorithm for determining the steady-state probability distribution of an ergodic system arbitrarily far from equilibrium. By enforcing equal sampling of different regions of phase space, as in umbrella sampling simulations of systems at equilibrium, low probability regions are explored to a much greater extent than in physically weighted simulations. The algorithm can be used to accumulate joint statistics for an arbitrary number of order parameters for a system governed by any stochastic dynamics. They demonstrate the efficiency of the algorithm by applying it to a model of a genetic toggle switch which evolves irreversibly according to a continuous time Monte Carlo procedure.

Umbrella sampling for nonequilibrium processes.

We use three Chandra observations, totaling 134.3 ks, to constrain the dynamical motion of NGC 1404 falling toward the dominant elliptical NGC 1399 through the Fornax Cluster gas. The surface brightness profile of NGC 1404 shows a sharp edge at ~8 kpc from its center in the direction of NGC 1399, characteristic of jumplike temperature and density discontinuities from ram pressure stripping of the galaxy gas, caused by its motion through the surrounding intracluster medium (ICM). We find that the temperature of the galaxy gas inside the edge is ~2.8 times cooler (kT = 0.55 keV with abundance A = 0.73 Z☉) than the cluster gas (kT = 1.53 keV, A = 0.42 Z☉). We use the shape of the surface brightness profile across the edge to fit the position of the edge, the power-law behavior of NGC 1404's density distribution in the leading direction, and the density discontinuity at the edge. The electron density inside the edge (3.9-4.3) × 10-3 cm-3 depends strongly on the gas abundance, while the density of the ICM (7-8) × 10-4 cm-3 depends strongly on the assumed geometry (relative distance) between NGC 1404 and NGC 1399. The corresponding pressure jump of 1.7-2.1 across the leading edge of the galaxy and the cluster free-stream region implies near sonic motion (Mach number 0.83-1.03) for NGC 1404 with a velocity 531-657 km s-1 relative to the surrounding cluster gas. The inclination angle of the motion, inferred using the relative radial velocity between NGC 1404 and 1399 as representative of that between NGC 1404 and the cluster ICM, is uncomfortably large (40°) given the sharpness of the surface brightness edge, suggesting either a nonzero impact parameter between NGC 1404 and 1399 or that NGC 1399 is also moving radially with respect to the cluster ICM.

http://iopscience.iop.org/article/10.1086/427548/pdf

Aryeh Warmflash

Papers

A method to recapitulate early embryonic spatial patterning in human embryonic stem cells

Multilineage Transcriptional Priming and Determination of Alternate Hematopoietic Cell Fates

Chandra Observations of NGC 4636-an Elliptical Galaxy in Turmoil

Umbrella sampling for nonequilibrium processes.

Infall of the Elliptical Galaxy NGC 1404 into the Fornax Cluster