THE POSSIBLE ROLE OF ALPHA-3-MELONCYTE, BETA-3-MELONCYTE AND GAMMA-3-MELONCYTE STIMULATING HORMONE-CONTAINING KERATINOCYTES IN THE INITIATION OF VITILIGO VULGARIS

By means of the indirect immunofluorescence assay, the skin of 16 viti ligo patient and 13 matched, normal, healthy controls was examined for MSH immunoreactivity. We found that the keratinocytes of involved ski n uninvolved and normal control skin contain alpha-, beta- and gamma 3 -MSH, but to different extents. The immunoreactivities of the MSHs wer e remarkably increased in involved skin and decreased in uninvolved sk in as compared to normal healthy volunteers. By examining adjacent sec tions, it was found that alpha-, beta-, and gamma 3-MSH-like immunorea ctivities coexist in immunoreactive for beta-MSH. Some positive extrac ellular granular material (EGM) could be noticed filling the intercell ular spaces among keratinocytes, however only in the vitiliginous invo lved/uninvolved biopsies. We suggest that the initial pathogenesis of vitiligo is due to a melanocyte malfunction, including a disturbance o f the MSH receptiveness, dependent on the overstimulation of melanocyt es from locally generated. MSHs as well as the abnormal accumulation ( = observed EGM) of extracellular MSHs. This might be contradictory to normal melanocyte function and may finally result in melanocyte destru ction. But it remains to be elucidated whether the increased MSH immun oreactivities in keratinocytes of involved skin is the primary cause f or epidermal melanocyte damage or a secondary consequence of malfuncti on of the MSH receptor on melanocytes.