Our immune system has many different types of specialized cells, and macrophages have to be my favorite. One look at our image today, and you’ll see why they are such amazing little workers.
Macrophages are white blood cells that engulf and ingest material as part of the immune response against pathogens. Macrophages have specialized receptors on their surface that identify the target and initiate the pathway leading to engulfment and ingestion. Past models have suggested that these receptors passively find and bind targets, but a recent paper shows that macrophages actively probe the extracellular environment for targets, especially when targets are sparse or moving quickly. In addition, this paper shows that these probing protrusions are actin-rich and are dependent on some known actin regulators. Images above are scanning electron micrographs of macrophages in the presence of beads that are treated to make them targets for macrophages. Protrusions are obvious in control cases (left and middle, arrows), but are absent in cases when actin is depolymerized by a drug called latrunculin B (right).
Flannagan, R., Harrison, R., Yip, C., Jaqaman, K., & Grinstein, S. (2010). Dynamic macrophage "probing" is required for the efficient capture of phagocytic targets originally published in The Journal of Cell Biology, 191 (6), 1205-1218 DOI: 10.1083/jcb.201007056
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