Locomotion of white blood cells: a biophysical analysis

We determined some biophysical properties of human granulocytes, monocytes, and lymphocytes in respect to their locomotion. Granulocytes were exposed to plasma and were allowed to crawl on uncoated or glycol methacrylate coated glass plates. Monocytes did not migrate on uncoated glass, but did so on glycol methacrylated glass. Lymphocytes did not move on glass or glycol methacrylated glass, but moved on plexiglas coverslips. Granulocytes and monocytes showed a pronounced, directed movement towards a lysed erythrocyte (necrotaxis), lymphocytes showed no necrotactic response. The information collected by the granulocytes and monocytes in the necrotactic gradient was between 1 and 2 bits. This small amount of information indicated that the cellular decision in favor of a new direction of migration is based on a mechanism involving instability. We showed that the necrotactic response of granulocytes and monocytes is the product of the chemokinetic activity and the polar order parameter (= McCutcheon index) indicating that the cellular decision for a new direction of migration is independent of the speed of the cell movement. The movement of monocytes can be characterized in a similar way to that of granulocytes: the angle of deviation from a straight line path is nearly a fixed value (+/- 35 degrees). Lymphocytes stay in a restricted area after straight line movement. Particular attention was focused on cellular properties involved in locomotion. The characteristic time of the internal clock controlling the locomotion was 0.9 minutes for granulocytes and 2 minutes for monocytes. We were not able to determine the characteristic time of lymphocytes. We were able to determine the internal program responsible for the change in direction of movement. The directional memory time for granulocytes was 0.9 minutes. Monocytes had two directional memory times, short (2 minutes) and long (greater than 18 minutes). Lymphocytes had a very short directional memory time of 40 seconds. The distribution of the track velocities of migrating granulocytes and monocytes was described by bell shaped curves indicating homogeneous populations of cells. The distribution for lymphocytes had two maxima.