Macrophages

The Russian bacteriologist Metchnikov described the macrophage for the first time in the late 19th century.1 For his extraordinary contributions to the then burgeoning field of immunology, he was one of the recipients of the 1908 Nobel Prize in Medicine or Physiology. The etymology of the word macrophage, built from the roots makros and phagein, lends insights into the earliest understanding of the function of these captivating cells, that is, the devouring of large structures. We now understand that these big eater macrophages engulf invading pathogens, as well as debris and dead and dying cells. However, beyond roles for these cells in phagocytosis, research has uncovered seminal functions for macrophages in diverse processes, such as development,2,3 metabolism,4 and reproduction.5 Once monocytes are recruited from the circulation into the target tissues, they are transformed into macrophages; these cells are both modulated by and modulate the fundamental phenotypes of the tissues into which they are …