These are moving schematic diatrams of the action of lung macrophages when confronted with different kinds of particles that can reach the deep lung. The macrophage is represented by the green blob, the particle or fiber in black, and the enzymes released by the macrophage in red in the final stages of the animation.
Click on the image to view the animation.
|Macrophage enveloping a particle. Many billions of such ordinary particles are inhaled into the deep lung with every breath. They can be enveloped as indicated here and safely removed from the lung. (Animated gif, 69 kB)|
|Macrophage enveloping a short fiber. Like ordinary particles, sufficiently short fibers can also be enveloped and safely removed from the lung, too. (Animated gif, 77 kB)|
|Macrophage attempting to envelope a long fiber. Long fibers are the only shape that can be inhaled to the deep lung if it is thin enough in diameter, but cannot be successfully enveloped by the macrophage if it is too long. This unsuccessful envelopment leads to the leakage of potent enzymes from the interior of the cell onto the surface of the lung with consequent lung damage that is thought to lead to lung disease including cancer. Such diseases do not develop if the long fibers can be removed rapidly from the deep lung by dissolution in the lung fluid.* (Animated gif, 70 kB)|
* Churg, Wright, Bilks, and Dai, "Pathogenesis of fibrosis produced by asbestos and man-made mineral fibers: What makes a fiber fibrogenic?". Inhalation Toxicology 12 (Suppl. 3), 15-26 (2000).