Fundamental research: The first ambition of the laboratory is to develop biophysical methodologies and concepts to decipher cell biology mechanisms. This fundamental research is mainly focused on the adaptive immune response mediated by the T lymphocyte. Essential steps of the lymphocyte activation and recruitment are explored at different scales from the molecules, where the functioning of the T cell receptor and the role of integrins and cytoskeleton are scrutinized, to the tissue scale, where the cell adhesion, activation and migration are analyzed in blood vessels an in inflamed tissues. This activity is described below as 4 main Thematics. The LAI also participates to different collaborative projects where its expertise is valorized in areas beyond immunology.

Transfer to medicine: The second ambition of the laboratory is to transfer its fundamental knowledge and know-how to medical applications. This transfer activity is mainly performed in the Lab facilities at university hospital “La Conception” in Marseilles, and consists either to investigate the mechanisms of a pathology with biophysical methods, or to apply novel methodologies for diagnosis and in vitro treatment testing . This activity is described in section ‘Clinical Transfer’.

Thematic 1: Adhesion and recognition at the molecular scale

Immune cells communicate via surface receptors controlling cell adhesion and signalling. Thus, immune receptors have to discriminate exquisitely molecules from self and non-self. Specific, reversible and force-sensitive ligand-receptor bonds are formed between the T cell receptor and MHC peptide, antigen and antibody as well as between adhesive receptors like integrins and their various ligands. We are deciphering these complex kinetics at the single molecule level with the aim of integrating them to understand collective effects at the cellular scale. For this, we develop and exploit different single molecule techniques, with a special expertise for laminar flow chamber, which, besides being a massively parallel technique, uniquely provide a control of interaction starting time. Our efforts contribute to unveil fundamental properties of these interactions as well as to exploit these concepts to design new therapeutic molecules.

Thematic 2:  T cell activation and mechano-transduction

Interactions with surfaces, either artificial or cellular, play a key role in the function of immune cells, and in particular for the T lymphocyte. Using receptor ligand interactions and cytoskeleton deformations, cells are exerting and feeling forces which are essential for the cells to understand the surrounding world, in order to (re)act adequately. This capacity to integrate and evaluate those mechanical signals is called mechanotransduction and its understanding is a major current challenge in cell biology and biophysics. We set to dissect this phenomena at single cell scale by a combination of approaches using original engineered substrates coupled to high resolution surface optical microscopy. We have also a strong expertise to exert and record forces at different scales of space and time, using force based biophysical techniques (atomic force microscopy, optical tweezers, micromanipulations, biomembrane force probe, flow chamber). We develop original setups to couple those to recording by fluorescence microscopy the activation state of the lymphocyte using calcium or phosphorylation probes. Using photoactivable molecules, we also directly play on mechanical organization of the cells.

Thematic 3: Leukocyte recruitment in quantified microenvironments

The remarkable ability of leukocytes to leave the blood stream, cross the vascular endothelium, and enter tissues or organs is critical for both the innate and adaptive immune response. A common mechanism for extravasation of circulating leukocytes is currently defined as a multi-step process including first selectin-mediated capture to and rolling along the vascular walls, then firm adhesion and speading mediated by integrin adhesion receptors, finally crawling along and transmigration across the vascular endothelium. To investigate the mechanisms and the pathological failures of this recruitment cascade, we develop in vitro assays to control quantitatively the cells microenvironment during each step of interest. These minimal in vitro systems are designed with microfluidics and micropatterning technologies. The main questions target the role of cells rheology, adhesion, mechanotransduction and chemical sensing on their extravasation toward infected or inflamed targets.

Thematic 4: Remodeling at the tissue level in infected organs

The human lung is the largest surface that is in continuous contact with the inhaled air, containing numerous innocuous environmental antigens, including allergens as pollen or house dust mite (HDM) particles. The immune system should normally not react to these harmless substances. On the other hand, the lung can be the entrance site for pathogens including viruses, bacteria and fungi, and to these, a vigorous immune response should be initiated. Recent studies suggest critical immunogenic and immunoregulatory functions of airway epithelium. Using several approaches (flow cytometry, fluorescence microscopies LSM and confocal), we try to decipher, in animal models, the cellular and molecular mecanisms of lung remodeling in inflammatory conditions.