Tattoo muncher

Melanophages are macrophages that patrol your skin acting as an important line of defence from pathogens and particles that can enter the body through cuts and scrapes. Their name comes from their appetite for melanosomes, small droplets of melanin, the skin pigment produced by melanocytes. When skin is tattooed, the ink pigments are a rainbow-coloured buffet for the melanophages. Despite this cartoon, tattoos generally last a lifetime so what happens, do the melanophages eat their fill? In humans it seems likely that, having eaten the ink, the melanophages remain at the same site acting as a reservoir of colour. Remember that these cells are a fraction of a millimetre in size so to them the thinnest tattoo line is like a football pitch to us. In case you were thinking of getting your pet hamster some kick-ass inkwork, the situation seems to be a bit different in animals. Macrophages generally have a shorter lifespan in mice. When they are tattoed the initial cells that ate the pigment die after a couple of weeks, this releases the particles which are eaten by neighbouring melanophages in a cannibalistic cycle that means the colouring persists. You can read more about it in this research paper [Baranska et al. 2018 J Exp Med. 215: 1115–1133].

Obviously melanophages didn’t evolve on the off chance that humans might one day start filling their dermis with ink. Like all macrophages they respond to a wide range of signals so that normally they defend and repair the body, in this case the skin. However, they have their dark side (regardless of eating melanin!) and the wrong response can lead to skin disease; they are frequently associated with melanoma. This is another example of where more research on regulation of macrophage behaviour will help us understand disease processes.

This design is available on a range of cool merchandise from my RedBubble store.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.