Three‐dimensional motility cycle in leukocytes

A 3‐dimensional dynamic image analyzing system (3D‐DIAS) has been developed in which a translocating cell is optically sectioned in the z‐axis within a 2 sec period; the perimeter of the cell in each section is digitized into the 3D‐DIAS data file, and the digitized perimeters are wrapped in order to reconstruct the cell image in three dimensions. Using 3D‐DIAS, we have obtained the first dynamic 3‐dimensional description of human polymorphonuclear leukocytes (PMN) translo‐cating on a glass surface. A general behavior cycle has emerged which includes two phases. In the first, an ellipsoidal PMN with significant z‐axis extends anteriorly and descends to the substratum. When the ventral surface of the anterior end contacts the substratum, there is rapid anterior expansion, which correlates with velocity peaks. In the second phase, the elongate PMN stops translocating along the substratum, the anterior end lifts off of the substratum, sometimes to heights greater than the length of the PMN at the substratum, and finally the PMN retracts into an ellipsoidal morphology still capable of random protrusions. During this second phase, which correlates with velocity troughs, turning usually occurs. The degree of turning is restricted by the continuous integrity of the posterior uropod. The period of the behavior cycle varies from roughly 0.5 to 2 min between PMNs, but is relatively constant within each individual PMN. © 1992 Wiley‐Liss, Inc.