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→Cells of the Epidermis
*'''Langerhans' cells'''
*'''Langerhans' cells'''
These are dentritic cells derived from bone marrow. They act as ''antigen presenting cells'' in the epidermis as part of the mononuclear phagocyte immune system. Langerhans' cells express MHC I and II molecules and immunoglubulin Fc receptors and are a key feature of '''delayed hypersensitivity responses.'''
These are dentritic cells derived from bone marrow. They act as ''antigen presenting cells'' in the epidermis as part of the mononuclear phagocyte immune system. Langerhans' cells express MHC I and II molecules and immunoglubulin Fc receptors and are a key feature of '''delayed hypersensitivity responses.'''
*'''Melanocytes'''
These are also dentritic cells and are derived from the neural crest. They are immersed in the epidermis where they form close contact with a defined number of keratinocytes - an '''epidermal-melanin unit'''. '''Melanin''' is composed of 2 types: ''eumelanin'' which is black-brown and ''phaeomelanin'' which is reddish-brown. Melanocytes produce pigment in melanosome structures which are membrane-bound structures involved in the transfer of pigment to keratinocytes. An important function of melanin is UV protection and absence of pigment confers increased sensitivity to UV damage.
===Dermis===
===Dermis===