Immunohistologic evaluation of the effect of cyclosporine treatment on the lichen planus immune infiltrate.

We have investigated immunohistologically the cutaneous immune infiltrate in the lesions of five patients with severe, extensive lichen planus of recent onset before and after 15 days of oral, low-dose cyclosporine therapy (3 mg/kg/day). Before therapy, we observed an abnormal bandlike cellular infiltrate localized in the papillary dermis, composed mostly of CD3+ cells, with a prevalence of CD4+ cells. Infiltrating lymphocytes showed markers of activation (HLA-DR antigens and interleukin 2 receptor), and there were many Langerhans (CD1+) cells in the dermal infiltrate. After 15 days of cyclosporine therapy, we observed a dramatic decrease in the total number of T cells and a corresponding decrease in interleukin 2 receptor-positive activated CD25+ cells and in antigen-presenting cells (CD1+ and CD14b+). These changes were concurrent with clinical improvement. Our results are compatible with the hypothesis that the inhibition of CD4 T cells by cyclosporine might explain the drug's therapeutic action and that the interaction between antigen-presenting cells and CD4 T cells is important in the pathogenesis of lichen planus.