RESUMEN
Abstract: Background: Pityriasis rosea is a common papulosquamous disorder. However, its etiology and pathogenesis remain unclear. Objective: We investigate the types of inflammatory cells infiltrating the lesional skin of pityriasis rosea and demonstrate whether T-cell-mediated immunity is involved in the pathogenesis of this condition or not. Methods: The biopsies were taken from the lesional skin of 35 cases of patients diagnosed with pityriasis rosea. The specimens were prepared in paraffin sections, then submitted to routine immunohistochemistry procedures using monoclonal antibodies directed against CD3, CD4, CD8, CD20 and CD45RO and horseradish peroxidase-labeled goat anti-human antibodies. The positive sections were determined by the ratio and staining intensity of positive inflammatory cells. Results: The mean score of positive CD3, CD4, CD8, and CD45RO staining was respectively 3.74±3.88, 5.67±4.40, 2.94±3.42 and 7.68±4.33 in these pityriasis rosea patients (P<0.001). The percentage of positive staining was 54.29% (19/35), 69.7% (23/33), 40% (14/35) and 79.41% (27/34) (P<0.05). However, the staining of CD20 was negative in all samples. The mean score of CD3 staining in patients with time for remission ≤60 days (4.90±4.21) was higher than that in patients with time for remission >60 days (2.00±2.5) (P<0.05), whereas no statistical difference in the mean score of CD4, CD8 and CD45RO staining was observed. study liMitations: The sample size and the selected monoclonal antibody are limited, so the results reflect only part of the cellular immunity in the pathogenesis of pityriasis rosea. Conclusion: Our findings support a predominantly T-cell mediated immunity in the development of pityriasis rosea.