Tech Talk #39: Pigment retention and the role of the macrophage!

Have you ever wondered how your cosmetic tattoos stay in the skin?

The skin is very good at rejecting all kinds of foreign matter. So, why doesn’t it just squeeze out the tattooed pigment?

Recent research has shown there is also a microscopic helper in the skin that stores the tattoo pigment and doesn’t eliminate it. We’re here to introduce you to the macrophage: what these cells are and why they’re important!

• Introducing the macrophage
• Retaining pigment: A process of capture & release

Introducing the macrophage!

Macrophages are a type of white blood cell providing crucial roles in the immune system. They exist within essentially all tissues to perform a main focus of patrolling for potential pathogens – they recognise cancer cells, microbes, cellular debris and foreign substances and engulf and digest them, a process called phagocytosis.

Fun fact: Macrophage is Greek for "big eater”!

Macrophages engulf and digest anything that does not have normal (healthy) proteins on the surface. This process of phagocytosis is the main defence against infection and injury once foreign matter has entered the body. Recent research has shown that the macrophage is the cell that stores cosmetic tattoo pigment.

Picture this!: Imagine lots of little ‘pac-men’ that gobble up the cosmetic tattoo pigment particles, each holding their own storage of pigment particles. These tiny little pac-men, our macrophages, are smaller than the diameter of a human hair and there are billions of them at work. Each macrophage will live for roughly three months.

Retaining pigment: A process of capture & release

So, how do tattoos stay put as individual macrophage cells die? A group of French scientists performed a study that showed even when macrophages die and release their pigment particles, other macrophages quickly gobble up the pigment, keeping it in place.

In cosmetic tattooing (and body art tattooing), macrophages see pigment particles as foreign invaders, engulfing the particles and trying to digest them. Unlike microbes, cellular debris, cancer cells and other biological material, the pigment particles are solid particles of chemicals that the macrophage cannot break down.

Scientific Figure from ResearchGate: Unveiling skin macrophage dynamics explains both tattoo persistence and strenuous removal.

A macrophage usually kills bacteria and viruses using acid, but it cannot 'kill' tattoo pigment. Another type of cell, the fibroblast can also absorb some ink particles. Together the macrophage and fibroblast bind pigment in the skin.

You can read more about this study: Baranska et al, Journal of Experimental Medicine, April 2018 https://pubmed.ncbi.nlm.nih.gov/29511065/

P.S. This continuous process of capture and release performed by the little pac-men (our macrophages) underscores why cosmetic tattoo and body tattoo removal can be such a difficult process – something we know all too well about

Stay posted for a specific Tech Talk on macrophages and pigment removal… coming soon!

This article has been written in partnership with Registered Training Organisation, THink Aesthetics (RTO 45188).

The content included is a short adapted extract from the unit  SHBBSSC004 Identify the Function and Structure of Skin and Hair for Cosmetic Tattooing from THink Aesthetics' Diploma of Cosmetic Tattooing.

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