Centriolar location during blood cell spreading and motion in vitro: an ultrastructural analysis.

Different motile blood cells behave differently on a glass surface. Macrophages go through all the stages of spreading described previously for fibroblasts; granulocytes become polarized after a short stage of radial spreading, while the polarization of lymphocytes takes place immediately upon attachment. The active centrioles of the cells we have studied orient their distal ends towards the upper cell surface. The centrioles in blood cells have a different location with respect to the nucleus and the leading edge of the cell: in macrophages the centrioles are situated mostly anterior to or at the side of the nucleus; in granulocytes they lie between the nuclear segments; and in lymphocytes they are positioned strictly posterior to the nucleus, in the uropod. In each case, however, the centrioles are localized in the central region of the cytoplasm. Their alignment does not appear to be related to the blood cells' random motion in vitro.