THE INTRACELLULAR-DISTRIBUTION PATTERNS OF MYOSIN AND ACTIN ARE DIFFERENT AMONG HUMAN NEUTROPHILS AND MONOCYTES DURING LOCOMOTION

Background and Objective. Neutrophils and monocytes initiate their cha racteristic ameboid movement by using mechanochemical systems of contr actile proteins. It is known that neutrophils and monocytes exhibit di ffering patterns of motility. We set out to determine whether these di fferences may be associated with the intracellular distribution of myo sin and actin, the principle components of the cellular apparatus invo lved in motility. Methods. Myosin and F-actin in human neutrophils and monocytes were observed at resting and motile stages by using a doubl e-fluorescence staining procedure and a confocal laser scanning micros cope. Results. In motile neutrophils, myosin was distributed in the la mellipodia and the cytoplasm, observed as a speckled pattern, whereas F-actin was concentrated in the front of the lamellipodia and in the p erinuclear area. In the motile monocytes, myosin was found in the wide lamellipodia and was seen to radiate from the cytoplasm towards the e dges of the cell in a punctate pattern. F-actin was densely distribute d along the leading edge of the wide lamellipodia as well as in the pe rinuclear region. No differences were apparent in the intracellular di stribution of myosin and F-actin between the resting neutrophils and m onocytes. Interpretation and Conclusions. Findings indicate that diffe ring patterns of arrangement of myosin and actin in the lamellipodia a nd cytoplasm of neutrophils and monocytes may contribute to their move ment, in vitro. (C) 1997, Ferrata Storti Foundation.