Melanocyte
A specialised cell in the skin that produces melanin, the pigment responsible for skin colour and UV protection. Melanocytes reside in the basal layer of the epidermis. MC1R on melanocytes is the target of afamelanotide, which stimulates eumelanin production.
Technical Context
Melanocytes reside in the basal layer of the epidermis at a density of approximately 1,000-2,000 per mm² (relatively constant across ethnicities — skin colour differences result from melanin type, amount, and distribution rather than melanocyte number). Each melanocyte services approximately 36 keratinocytes through dendritic processes — the epidermal melanin unit. Melanin is synthesised in specialised organelles called melanosomes, which are transferred to surrounding keratinocytes via dendritic tips. Melanosome transfer mechanisms: cytocrine secretion (membrane fusion), phagocytosis (keratinocytes engulf melanosome-containing dendritic tips), and exocytosis/endocytosis (melanosomes released extracellularly then taken up). In darker skin, melanosomes are larger, more numerous, and distributed individually throughout keratinocytes; in lighter skin, they are smaller, fewer, and clustered. Afamelanotide stimulates both melanogenesis within melanosomes and melanosome transfer to keratinocytes.