LYMPHOCYTE AND MACROPHAGE SUBSETS IN ACTIVE AND INACTIVE LESIONS OF LICHEN-PLANUS

Lichen planus (LP) is a mucocutaneous disease for which the etiology a nd pathogenesis are poorly understood. We performed an immunohistochem ical study on formalin-fixed tissue sections of 10 cases of LP using s ubsets of antibodies to lymphocytes (LCA, CD3, OPD4-CD4, L26, LN1 and Leu-7), and monocyte-macrophages [lysozyme, KP1-Mac, Factor XIIIa (FXI IIa) and S-100 protein]. Six cases showed typical histological feature s of active LP, two cases showed features of active and inactive LP, a nd two cases showed only inactive LP. In active LP, scattered T cells (CD3+ and pan T cells) were present in the epidermis, whereas large nu mbers of CD3+ T cells were present at the dermoepidermal junction and in the dermis. Approximately 40% of the T cells at the dermoepidermal junction were of the helper/inducer subset, whereas approximately 80% of those in the dermis were CD4 positive (helper/inducer T cells). Occ asional B cells were present in the dermis only. Increased numbers of S-100-positive Langerhans cells, macrophages expressing lysozyme, and FXIIIa dendritic cells were present in the epidermis and dermis. The i nactive lesions showed the presence of a few epidermal Langerhans cell s and a mild infiltrate of T cells (helper/inducer subset). These resu lts suggest that in addition to different subsets of T cells and macro phages, including Langerhans cells, dermal dendritic cells expressing Factor XIIIa and lysozyme-positive histiocytes play an important role in lichen planus. They may participate in the destruction and subseque nt regeneration of the basal layer of the epidermis, or alternatively may be activated as a result of destruction of the basement membrane i n LP.