P-15   MELANOCYTES AND LANGERHANS CELLS IN HAIR BULBS OF PIGMENTARY HAIR DISORDERS

KH Yoon, SH Sohn*, E-S Lee. Department of Dermatology, and Department of Laboratory of Cell Biology*, Ajou University School of Medicine, Suwon, Korea.

Background: Melanocytes in hair bulbs actively produce melanin pigment, which react with NKI/beteb, HMB45, tyrosinase, and TRP-1/2, whereas melanocytes in outer root sheath do not produce melanin pigment in resting state. In gray hairs, hair bulb melanocytes have no tyrosinase mRNA, and do not react with NKI/beteb, which represent some impairment of melanin production. Therefore the changes of melanocytes in hair bulbs are considered as a principal factor for pigmentary abnormalities of hairs. Langerhans cells are known to be normally found in hair bulbs only in telogen hairs, which work as either scavengers to remove unnecessary melanin pigment, or immune cells reacting with CD4+ T cells and B cells in alopecia areata hairs. Method: Hair bulbs from two patients with alopecia areata and another two patients with segmented heterochromia were observed under transmission electron microscope. Results: 1) Melanocytes of regrowing white hairs of alopecia areata and affected anagen hairs of segmented heterochromia showed increased electron density of nuclei, and margination of chromatin, which looked similar with apoptosis or dark cell transformation. Melanosomes were very heterogenous in their shapes, sizes and electron-densities. Namely, the changes of melanocytes in hair bulbs might induce abnormal melanosome production and, in turn, the pigmentary abnormalities in hair shafts. 2) Langerhans cells were present in the hair bulbs of anagen hairs as well as telogen hairs. Most of them did not have captured melanin pigment in their cytoplasm. They directly contact with melanocytes or lymphocytes infiltrating in hair bulbs. It may represent that Langerhans cells are important as immune cells rather than scavengers in these two kinds of hair disorders. In conclusion the pigmentary abnormalities of hairs of alopecia areata and segmented heterochromia might be induced by impairment of melanin production in melanocytes, which were affected by an immunologic mechanism related with Langerhans cells.