Two binding sites for Ki67 related to quiescent and cycling cells in human epidermis.

The monoclonal antibody Ki67 (Ki67) binds to a nuclear antigen expressed by cycling cells of several human tissues and to the cytoplasm of the basal layer cells of squamous epithelia. We have used an immunohistochemical method to visualize the binding sites of Ki67 in normal and hyperproliferative epidermis. Cytoplasmic staining was present in the basal layer cells of normal epidermis, but was decreased in psoriatic and post-tapestripping epidermis. In sections of normal epidermis only a small minority of nuclei were positive, but sections of psoriatic epidermis and epidermis 40 and 48 h after tapestripping showed large numbers of positive nuclei in the basal and suprabasal layers. Since recent reports strongly suggest that the cell production rate is regulated by changes in the number of cycling cells, the hypothesis that Ki67 binds also in human epidermis to the nuclei of cycling cells is supported by the present findings.