ANALYSIS OF CELL FLUX IN THE PARALLEL-PLATE FLOW CHAMBER - IMPLICATIONS FOR CELL CAPTURE STUDIES

The parallel plate flow chamber provides a controlled environment for determinations of the shear stress at which cells in suspension can bi nd to endothelial cell monolayers. By decreasing the flow rate of cell -containing media over the monolayer and assessing the number of cells bound at each wall shear stress, the relationship between shear force and binding efficiency can be determined. The rate of binding should depend on the delivery of cells to the surface as well as the intrinsi c cell-surface interactions; thus, only if the cell flux to the surfac e is known can the resulting binding curves be interpreted correctly. We present the development and validation of a mathematical model base d on the sedimentation rate and velocity profile in the chamber for th e delivery of cells from a flowing suspension to the chamber surface. Our results show that the flux depends on the bulk cell concentration, the distance from the entrance point, and the flow rate of the cell-c ontaining medium. The model was then used in a normalization procedure for experiments in which T cells attach to TNF-alpha-stimulated HUVEC monolayers, showing that a threshold for adhesion occurs at a shear s tress of about 3 dyn/cm(2).