Antigen Ki-67 is a non-histone nuclear protein, closely connected with cell proliferation. Determining Ki-67 allows for a quick and reliable evaluation of the growth fraction of the studied cell population. It serves as a marker of proliferative activity in neoplasms and other diseases with excessive cell proliferation such as psoriasis.

Evaluation of Ki-67 expression in epidermal cells was performed in 10 individuals suffering from plaque psoriasis, before and after one of three methods of phototherapy: broadband UVB, narrowband UVB or PUVA.

We observed increased Ki-67 antigen expression in psoriatic lesions. The percentage of Ki-67 positive nuclei in the epidermis affected by the disease ranged from 0 to 30% and in the macroscopically healthy surrounding tissue the percentage was from 0 to 10%.

After phototherapy the expression in lesional skin decreased (p < 0.01). The greatest decrease was observed after the application of PUVA therapy (from 25 to 10% of cells, p < 0.05). No significant differences were observed in the perilesional skin with regard to Ki-67 antigen expression before or after phototherapy.

On the basis of our own study and studies conducted by other researchers, it can be concluded that reduced Ki-67 expression after the application of PUVA and UVB therapies in the psoriatic epidermis is not a characteristic result of phototherapy only. It is a characteristic property of any effective psoriasis therapy.