Certainly the cells of the immune system are in constant communication, and are capable of rather dramatic forms of cooperation. For example, if a macrophage needs to expand its supply of cell-killing digestive enzymes, all it has to do is gobble up a neutrophil and add the neutrophil’s stockpile of enzymes to its own. So the immune system seems to qualify as a “system,” but does it possess the autonomy we expect to find in a “living entity”? If so, we should probably call the nervous system a kind of living entity too, since it is capable of plotting and carrying out the death of the
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