This video is taken from a 16-mm movie made in the 1950s by the late David Rogers at Vanderbilt University. It was given to me via Dr. Victor Najjar, Professor Emeritus at Tufts University Medical School and a former colleague of Rogers. It depicts a human polymorphonuclear leukocyte (neutrophil) on a blood film, crawling among red blood cells, notable for their dark color and principally spherical shape. The neutrophil is "chasing" Staphylococcus aureus microorganisms, added to the film. The chemoattractant derived from the microbe is unclear but may be complement fragment C5a, generated by the interaction of antibodies in the blood serum with the complement cascade, and/or bacterial N-formyl peptides. Blood platelets adherent to the underlying glass are also visible. Notable is the characteristic asymmetric shape of the crawling neutrophil with an organelle-excluding leading lamella and a narrowing at the opposite end culminating in a "tail" that the cell appears to drag along. Contraction waves are visible along the surface of the moving cell as it moves forward in a gliding fashion. As the neutrophil relentlessly pursues the microbe it ignores the red cells and platelets. However, its leading edge is sufficiently stiff (elastic) to deform and displace the red cells it bumps into. The internal contents of the neutrophil also move, and granule motion is particularly dynamic near the leading edge. These granules only approach the cell surface membrane when the cell changes direction and redistributes its peripheral "gel." After the neutrophil has engulfed the bacterium, note that the cell's movements become somewhat more jerky, and that it begins to extend more spherical surface projections. These bleb-like protruberances resemble the blebs that form constitutively in the M2 melanoma cells missing the actin filament crosslinking protein filamin-1 (ABP-280) and may be telling us something about the mechanism of membrane protrusion.
Thomas P. Stossel (Brigham and Women's Hospital and Harvard Medical School), June 22, 1999
Edited by lyok, 03 September 2011 - 09:12 AM.