A POSSIBLE ROLE FOR LANGERHANS CELLS IN THE REMOVAL OF MELANIN FROM EARLY CATAGEN HAIR-FOLLICLES

Hair pigmentation is coupled to the hair follicle growth cycle. A comm on feature of catagen is the translocation of melanin from the matrix to the dermal papilla of the hair follicle. However, the mechanism whe reby this pigment, not incorporated into the hair shaft, is removed fr om the hair bulb during early catagen is poorly understood. Routine ul trastructural examination of four normal scalp specimens revealed a ra re hair follicle in early catagen. Close study of the hair bulb of thi s catagen follicle revealed a Langerhans cell in the process of transf erring pigment from the matrix to the dermal papilla. This cell also c ontained numerous characteristic Langerhans granules (LG) (also known as Birbeck granules). Interestingly, these granules were intimately as sociated with melanosomes: so intimate, in fact, that melanosomes appe ared to have been endocytosed by LG. This unique demonstration of remo val of hair follicle melanin by Langerhans cells during early catagen and of pigment uptake by Langerhans cells by endocytosis into LG, sugg ests one way by which 'unused' pigment can be removed from the hair fo llicle during catagen.