A. Norris et al., THE EXPRESSION OF THE C-KIT - RECEPTOR BY EPIDERMAL MELANOCYTES MAY BE REDUCED IN VITILIGO, British journal of dermatology, 134(2), 1996, pp. 299-306
The proto-oncogene c-kit encodes the transmembrane tyrosine kinase rec
eptor that has a role in the growth regulation of various cell types i
ncluding melanocytes. In the present study we have examined the expres
sion of the c-kit protein in the skin of seven patients with vitiligo,
Melanocytes positive for c-kit protein were observed in the basal lay
er in non-lesional skin and the mean number of 25.8 +/- 5.2 (per 200 b
asal cells) compared with that of 21.8 +/- 3.5 from six control subjec
ts. In perilesional skin there was a reduction in the numbers of c-kit
positive melanocytes (6.7 +/- 2.6) and this was especially noticeable
in six of the seven patients. Such a reduction was less obvious follo
wing staining with MEL-5 and in only two subjects were the numbers of
melanocytes below the normal range. This suggests that the reduction i
n c-kit staining was the result of decreased expression of the protein
rather than a loss of melanocytes. No melanocytes, positive for c-kit
protein, or after staining with MEL-5, were identified in lesional sk
in although isolated tyrosinase-positive melanocytes were seen in one
subject. There was no apparent change in the numbers of mast cells exp
ressing c-kit protein and the intensity of staining in the dermis even
in lesional skin was similar to that in the controls. These results d
emonstrate that c-kit protein is present on melanocytes in adult human
skin and that in perilesional skin of some vitiligo patients there is
a reduction in the numbers of melanocytes expressing this receptor, W
hether this may contribute to the defective melanocyte growth and/or s
urvival that occurs in vitiligo or whether it is a consequence of mela
nocyte damage remains to be seen.