Functions of neutrophil motility of human blood: locomotion and chemotaxis in simplified systems

Polymorphonuclear leukocytes (PMN, granulocytes) employ their plasma membranes and subjacent microfilament-rich peripheral cytoplasm for such motile functions as adherence and spreading, random locomotion, chemotaxis (directed locomotion), and phagocytosis. All of these functions are preserved in certain anucleate, granule-poor, cytoplasmic fragments (cytoplasts) derived from PMN. Thus, the sensing, transduncing, and effector capacities involved in these functions remain integrated without control from nuclei or from the other cellular organelles left behind when the cytoplast forms. More recently, we have begun to examine in intact PMN the role of divalent cations, which have been thought to be essential for motile function of leukocytes in general, and for the function of critical adhesion molecules in particular. In slide preparations under direct microscopic observation, EDTA (10 mM; to chelate divalent cations) did not impair either random locomotion or chemotaxis, nor did specific antibodies to beta-2 (CD 18) integrins or to other PMN integrins. Motile behavior appeared to benefit from the close approximation of slide and coverslip ("chimneying"). Thus, in "close quarters", PMN can generate the force for locomotion even when adhesion molecules are lacking or disabled. We relate these findings to the reported independence from integrins of PMN in certain experimental and diseases states.