A numerical method to solve the Stokes problem with a punctual force in source term

The aim of this note is to present a numerical method to solve the Stokes problem in a bounded domain with a Dirac source term, which preserves optimality for any approximation order by the finite-element method. It is based on the knowledge of a fundamental solution to the associated operator over the whole space. This method is motivated by the modeling of the movement of active thin structures in a viscous fluid.Comment: Comptes Rendus M{\'e}canique, Elsevier, 2015, http://www.sciencedirect.com/science/article/pii/S163107211400181

Une méthode numérique pour la résolution du problème de Stokes avec une force ponctuelle en terme source.

International audienceThe aim of this note is to present a numerical method to solve the Stokes problem in a bounded domain with a Dirac source term, which preserves optimality for any approximation order by the finite-element method. It is based on the knowledge of a fundamental solution to the associated operator over the whole space. This method is motivated by the modeling of the movement of active thin structures in a viscous fluid.Le but de cette note est de présenter une méthode numérique pour la résolution du problème de Stokes avec une force ponctuelle en terme source, qui assure l’optimalité de l’erreur d’approximation éléments finis. Elle s’appuie sur la connaissance explicite d’une solution fondamentale de l’opérateur linéaire associé. Cette méthode est motivée par la modélisation du mouvement de structures fines actives dans un fluide visqueux

LFA-1 nanoclusters integrate TCR stimulation strength to tune T-cell cytotoxic activity

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Kinetic measurements of human CD8+ T cell cytotoxic activity in a 384-well plate format

Chapitre 8International audienceThe elimination of infected or cancerous cells by CD8+ cytotoxic T lymphocytes (CTL) is a crucial effector mechanism of the immune system. Upon antigen recognition, CTL stop migrating, establish a tight contact with target cells and deliver cytotoxic molecules such as perforin and granzymes that lead to target cell apoptosis. The ability of CTL to control a population of infected cells or a tumor depends on multiple parameters, such as the relative numbers of CTL and target cells, the intrinsic cytotoxic activity of CTL, the intrinsic resistance of target cells and the repertoire of immune checkpoints tuning cytotoxic activity at the CTL:target cell interface. In this context, in vitro assays to precisely measure CTL:target cell interactions and cytotoxic activity over time are required to monitor natural or therapeutic responses. We here present an image-based method that allows recording of positions and survival of CTL and target cells over time in a high-throughput format. The protocol relies on the staining of CTL and target cells with fluorescent dyes and the automated imaging of cells deposited in wells of a 384-well plate with an automated cell imaging device. We discuss potential applications offered by the kinetic assessment of CTL cytotoxic activity in a high-throughput format

Molecular Tuning of Actin Dynamics in Leukocyte Migration as Revealed by Immune-Related Actinopathies

International audienceMotility is a crucial activity of immune cells allowing them to patrol tissues as they differentiate, sample or exchange information, and execute their effector functions. Although all immune cells are highly migratory, each subset is endowed with very distinct motility patterns in accordance with functional specification. Furthermore individual immune cell subsets adapt their motility behaviour to the surrounding tissue environment. This review focuses on how the generation and adaptation of diversified motility patterns in immune cells is sustained by actin cytoskeleton dynamics. In particular, we review the knowledge gained through the study of inborn errors of immunity (IEI) related to actin defects. Such pathologies are unique models that help us to uncover the contribution of individual actin regulators to the migration of immune cells in the context of their development and function