The body is sometimes compared to the Universe. This is not a hollow metaphor; indeed, there are a hundred times more cells in your body than there are stars in the Milky Way, and it totally true that nearly all the elements in the human body were made in stars that have come through several rounds of explosion in what is called supernova explosions. But there’s more! Our body’s immune system contains swarms of white blood cells called that attack pathogens in clusters that looks like a microscopic version of a real supernova (see the time lapse video clip below).
What may look like an exploding star or supernova is actually calcium signals pulsing through the human immune system. These signals are emitted by neutrophils, a type of white blood cells that helps the body fight infection. When microorganisms, such as bacteria or viruses, enter the body, neutrophils are one of the first immune cells to respond. They travel to the site of infection, where they destroy the microorganisms by ingesting them and releasing enzymes that kill them.
Neutrophils work best in teams or clusters. As neutrophil cells migrate towards a site of infection, they trigger calcium pulses to recruit more neutrophils, increasing the effectiveness of wound sealing or pathogen clearance. However, over-clustering has downsides (e.g., may cause tissue inflammation). So the cells also trigger a delayed inhibitory signal that slows down the propagation of the inflammatory signals, keeping a balance as it were between the urgency to fight and the wisdom of “backing off”.
New Scientist; Proceedings of the National Academy of Sciences, U.S.