Using magnetic twisting cytometry to study monocyte activation

Circulating monocytes are key blood cells in a variety of disorders of the immune system. They are critically involved in the development of atherosclerotic lesions due to their ability to leave the blood stream and differentiate into macrophages upon entering sub-endothelial space. Prior to leaving the blood stream, a combination of chemokines triggers activation pathways which result in an increased expression of integrins. We are investigating whether the activation-dependent recruitment of integrins influences the mechanical properties of the cells. Besides getting new insights into basic cellular mechanics, this research also aims to lay the foundation for future cell biosensors for the diagnosis of cardiovascular disease. We have immobilized human monocytic leukemia cells (THP-1 cells) on glass substrates that support binding via the Fc-receptor. The viscoelastic properties of the cells were quantified by exerting a sinusoidal torque via magnetic particles bound to membrane protein CD14. We recorded the translational response of single cells and deduced the storage and loss moduli of THP-1 cells for several orders of magnitude of the actuation frequency. We will present the influence of pro-inflammatory ligands on the viscoelastic properties of the cells.