The adherence of human Fc receptor-bearing lymphocytes to antigen- antibody complexes. II. Morphologic alterations induced by the substrate

The adhesion of human Fc receptor-bearing lymphocytes to immobilized antigen-antibody complexes is accompanied by marked alterations in cell shape, resulting in flattening of greater than 90% of the adherent cells. In addition, about 65% of the adherent cells become elongated, with distinct uropods being present in about 1/3 of these cells. Scanning electron microscopy demonstrates that most of the surface microvilli are lost, while ruffled membranes and long microextensions are formed during the shape change. Time-lapse cinematography shows that the major shape changes occur within a few minutes after contact with the substrate, and that the adherent cells undergo translational motility. Both flattening and elongation of the adherent cells are inhibited by low temperature, chelating agents, cytochalasin B, and vinblastine, while sodium azide selectively inhibits elongation and uropod formation. It is argued that these morphological changes result from an active response of the cell to the immobilized complexes, and that such alterations may be related mechanistically to the ability of the cells to kill antibody-coated target cells.