The phenomenology itself is decades old. Neutrophil migration was observed in the early part of the 20th century, and was captured on film 50 years ago by the late David Rogers of Vanderbilt University. (Rogers' film can be viewed on the Web at: expmed.bwh.harvard.edu/projects/motility/neutrophil.html.) This film shows in dramatic fashion a neutrophil chasing a bacterium that is laying down a chemoattractant gradient--most likely the bacterial peptide f-MLP, which is induced by elements of the host immune system. A neutrophil tracks down the chemoattractant's source, moving in a polar fashion, leading with one end, retracting the other, and quickly changing course as the bacterium itself changes direction; all features of the chemotactic response that researchers are trying to get a handle on.
Genetic dissection of the protein pathways involved in slime mold chemotaxis is more advanced than neutrophils, since knocking out genes is relatively straightforward. Research on slime mold, for example, ...
