Melanosome complexes and melanin macroglobules in normal human skin.
The presence of melanin macroglobules, and sometimes that of melanosome complexes also, in epidermal melanocytes has been considered a feature of various skin diseases. Opinions differ as to whether these structures can occur in normal skin. We have studied these melanin inclusions in normal Caucasian skin in the entire soma of 116 melanocytes and the occurrence of melanosomes in phagosomes of 77 Langerhans' cells obtained in different seasons. During winter the melanocytes contained few melanosomes but many melanosome complexes and melanin macroglobules. These melanosome inclusions were in 86%, localized in the most basal part of the melanocytes, particularly in the dermal protrusions. It is suggested that these structures can be transferred from epidermal melanocytes to dermal cells and that melanin macroglobules derive from melanosome complexes. Irrespective of the season, most of the Langerhans' cells contained melanosomes in their phagosomes, which suggests a phagocytic capacity of these cells and a role in the elimination of the melanin.