Basigin is a glycosylated transmembrane protein belonging to the immunoglob
ulin superfamily. It is thought to play roles in intercellular recognition
involved in cell differentiation. We previously demonstrated at the light m
icroscope level a correlation between basigin expression and epidermal diff
erentiation. In the present study, the ultrastructural localization of basi
gin in normal human epidermal keratinocytes was investigated by immunoelect
ron microscopy. The basigin labeling was strongest on membranes of basal ce
lls, weaker on prickle cells, and absent in granular and horny cells. On th
e membrane of basal cells, labeling was observed on the apical and lateral
sides but not on the dermal side. Gold particles were mostly observed on th
e surface of microvilli, especially on their tips. There were fewer on the
intermicrovillous membrane and they were absent on the desmosome. These res
ults are consistent with our previous report that basigin expression is cor
related with differentiation of epidermal keratinocytes. Microvilli on basa
l and suprabasal keratinocytes might play roles in the differentiation of k
eratinocytes through basigin on the tips of microvilli.