Lymph node topology dictates T cell migration behavior

Adaptive immunity is initiated by T cell recognition of foreign peptides presented on dendritic cells (DCs) by major histocompatibility molecules. These interactions take place in secondary lymphoid tissues, such as lymph nodes (LNs) and spleen, and hence the anatomical structure of these tissues plays a crucial role in the development of immune responses. Two-photon microscopy (2PM) imaging in LNs suggests that T cells walk in a consistent direction for several minutes, pause briefly with a regular period, and then take off in a new, random direction. Here, we construct a spatially explicit model of T cell and DC migration in LNs and show that all dynamical properties of T cells could be a consequence of the densely packed LN environment. By means of 2PM experiments, we confirm that the large velocity fluctuations of T cells are indeed environmentally determined rather than resulting from an intrinsic motility program. Our simulations further predict that T cells self-organize into microscopically small, highly dynamic streams. We present experimental evidence for the presence of such turbulent streams in LNs. Finally, the model allows us to estimate the scanning rates of DCs (2,000 different T cells per hour) and T cells (100 different DCs per hour)

Большевик. 1932. № 107

This essay aims to clarify the debate over same-sex unions by comparing it to the fourth-century conflict concerning the nature of Jesus Christ. Although some suppose that the council of Nicaea reiterated what Christians had always believed, the Nicene theology championed by Athanasius was a dramatic innovation that only won out through protracted struggle. Similarly, despite the widespread assumption that Christian tradition univocally condemns homosexuality, the concept of sexuality is a nineteenth-century invention with no exact analogue in the ancient world. Neither heterosexuality nor homosexuality is addressed directly in Christian tradition; for this reason, the significance of older authorities for the modern debate is necessarily indirect. The dichotomy between progressive and conservative positions is therefore misguided: it is necessary neither

Prevalence and infection intensity of <i>Bd</i> from eight sites in Cameroon.

Prevalence (with 95% confidence intervals) and infection intensity, mean and standard deviation (SD), is reported for Campo Ma’an (CM), Ebo Forest (EF), Lobéké National Park (LB), Mbam Djerem National Park (MD), Mount Cameroon (MC), Mount Cameroon Village (MCV), Ndikiniméki (ND), and Takamanda (TM).</p

Distribution modeling and lineage diversity of the chytrid fungus <i>Batrachochytrium dendrobatidis</i> (<i>Bd</i>) in a central African amphibian hotspot

<div><p>The amphibian disease chytridiomycosis in amphibians is caused by the chytrid fungus <i>Batrachochytrium dendrobatidis</i> (<i>Bd</i>) and has resulted in dramatic declines and extinctions of amphibian populations worldwide. A hypervirulent, globally-dispersed pandemic lineage (<i>Bd</i>-GPL) is thought to be largely responsible for population declines and extinctions, although numerous endemic lineages have also been found. Recent reports of amphibian declines have been linked to the emergence of <i>Bd</i> in Cameroon, a major hotspot of African amphibian diversity. However, it is not known whether <i>Bd</i>-GPL or other lineages have been found in this region. This study therefore aims to examine <i>Bd</i> lineage diversity in the region and predict the distribution of this pathogen under current and future climate conditions using data from this study and from historical records. Almost 15% (52/360) of individuals tested positive for <i>Bd</i> using a standard quantitative PCR diagnostic. Infected amphibians were found at all eight sites sampled in this study. Species distribution models generated in BIOMOD2 indicate that areas with highest predicted environmental suitability occur in the Cameroon highlands and several protected areas throughout the country. These areas of high environmental suitability for <i>Bd</i> are projected to shift or decrease in size under future climate change. However, montane regions with high amphibian diversity are predicted to remain highly suitable. Phylogenetic analysis of the ITS sequences obtained from a set of positive <i>Bd</i> samples indicate that most fall within the <i>Bd</i>-GPL lineage while the remainder group with isolates from either Brazil or South Korea. Although more in depth phylogenetic analyses are needed, identification of <i>Bd</i>-GPL lineages in areas of high amphibian diversity emphasizes the need to continue to monitor for <i>Bd</i> and develop appropriate conservation strategies to prevent its further spread.</p></div