What's the matter with HIV-directed killer T cells?

That HIV-specific cytotoxic T-lymphocytes (CTLs) might be defective in some way has stimulated much controversy and research. We use mathematical models to explore the predictions of two competing CTL-defect theories: "defective memory" and "defective activation". We discuss whether these models are consistent with adoptive-transfer experiments in HIV-infected patients and vaccine trials in simian immunodeficiency virus (SIV)-infected monkeys. Finally, we describe experimental tests that could decide among these two theories and a competitor: CTL exhaustion.     

Does the Bicoid gradient matter?

The generation and interpretation of positional information are key processes in developmental systems. In this issue, Chen et?al. report discoveries made in the Drosophila embryo that give new insights into how positional information can be produced by patterning gradients.     

Leukocyte Adhesion: What's the Catch?

A recent study shows that the leukocyte adhesion molecules known as selectins form 'catch' bonds, the dissociation rate of which decreases with increasing applied force. The ability of selectins to switch between catch and slip bonds, where dissociation increases with force, can explain the shear threshold effect, in which leukocyte adhesion goes through a maximum with increasing shear rate.     

What's on the horizon for macroecology?

Over the last two decades, macroecology – the analysis of large‐scale, multi‐species ecological patterns and processes – has established itself as a major line of biological research. Analyses of statistical links between environmental variables and biotic responses have long and successfully been employed as a main approach, but new developments are due to be utilized. Scanning the horizon of macroecology, we identified four challenges that will probably play a major role in the future. We support our claims by examples and bibliographic analyses. 1) Integrating the past into macroecological analyses, e.g. by using paleontological or phylogenetic information or by applying methods from historical biogeography, will sharpen our understanding of the underlying reasons for contemporary patterns. 2) Explicit consideration of the local processes that lead to the observed larger‐scale patterns is necessary to understand the fine‐grain variability found in nature, and will enable better prediction of future patterns (e.g. under environmental change conditions). 3) Macroecology is dependent on large‐scale, high quality data from a broad spectrum of taxa and regions. More available data sources need to be tapped and new, small‐grain large‐extent data need to be collected. 4) Although macroecology already lead to mainstreaming cutting‐edge statistical analysis techniques, we find that more sophisticated methods are needed to account for the biases inherent to sampling at large scale. Bayesian methods may be particularly suitable to address these challenges. To continue the vigorous development of the macroecological research agenda, it is time to address these challenges and to avoid becoming too complacent with current achievements.     

What's all the noise about developmental stochasticity?

In October 2010, researchers from diverse backgrounds collided at the historic Cumberland Lodge (Windsor, UK) to discuss the role of randomness in cell and developmental biology. Organized by James Briscoe and Alfonso Marinez-Arias, The Company of Biologists' workshop was the latest in a series of meetings aimed at encouraging interdisciplinary interactions between biologists. This aim was reflected in talks at this workshop that ranged from the tissue to the cellular scale, and that integrated experimental and theoretical approaches to examining stochastic behavior in diverse systems.