Contribution of whole-cell optimization via cell body rolling to polarization of T cells.

Directed secretion of cytotoxins or cytokines by T cells during immune response depends on migration of the centrosome in the T cell to the interface with the target cell. The mechanism of the centrosome translocation has been elusive. The presented computational analysis demonstrates that the centrosome should be positioned at the interface if the T cell attempts simultaneously (a) to minimize its surface area, (b) to maximize the interface area, (c) to maintain the cell volume and (d) to straighten the microtubules. Live three-dimensional microscopy and measurements show that the optimal position of the centrosome is achieved in large part (by about 40%) via rolling of the entire T cell body on the target surface; this movement appears to entrain the centrosome. The theoretical and experimental results draw attention to the previously unrecognized role of the whole-cell structure and whole-cell movements in the T cell polarization.