Long-term chemotaxis of neutrophils in stable gradients: preliminary evidence of periodic behavior.

We observed and recorded the behavior of human neutrophils in stable linear gradients of the chemotactic attractant f-Met-Leu-Phe in a recently developed, direct-viewing, chemotaxis chamber. The cells were kept cold for the first hour after setting up the chemotaxis chamber in order to establish a stable gradient before allowing the cells to spread and begin to move by warming them up to 37 degrees C. We found that the cells showed very significant chemotaxis at different times throughout the 2-hour period of observation but, unexpectedly, the activity occurred in periodic or quasi-periodic cycles during which the cells entered phases of undirected motility lasting for several minutes. We discuss whether the periodicity is a population or single cell-based phenomenon and briefly speculate on its possible analogy to the well-known periodic chemotaxis of slime mould amoebas.