A common feature of melanocytes, Langerhans cells, and Merkel cells is that:
Melanocytes are residing in the basal layer of epithelium. Langerhans cells are found in the upper layer of skin and mucosal  epithelium restricted to zones of ortho keratinization. Merkel cells are also present among basal cells.
Produce melanin.
Have a low or no desmosomal attachment with surrounding keratinocytes.
All are dendritic cells.
All are pressure sensitive.