The possibility of distinguishing a subset of antigen-presenting cells from macrophages by means of anti S-100 protein sera. Dermal infiltrate of lichen planus as a model.

Macrophages may be distinguished from interdigitating cells and from Langerhans cells in paraffin sections, the latter cells being positive when an antiserum against brain S-100 protein is used. This antiserum was utilized to conduct a retrospective analysis of 10 cases of lichen planus, including both early and late lesions. In addition, staining of macrophages was carried out by means of anti-lysozyme, anti-alpha-1-antitrypsin and anti-alpha-1-antichymotrypsin. The anti-S-100 protein staining by immunoperoxidase methods showed large numbers of positive cells. Few macrophages were noted in the early lesions, but the ratios were reversed in the older lesions, in which macrophages predominated over dermal S-100-positive cells. Both Langerhans cells-interdigitating cells and macrophages could play important roles in various cutaneous disorders. The involvement of Langerhans cells-interdigitating cells or, on the other hand, of macrophages could distinguish among different pathological processes. Even in different evolutionary stages of the same lesion, as lichen planus, a different Langerhans cells-interdigitating cells/macrophages ratio could be important in explaining the pathogenetic development of the disease.