Immunohistochemical study of lichen planus.

The distribution of IgM and IgG in 20 cases of lichen planus and five cases of non-specific inflammation were studied by the unlabelled antibody-enzyme (PAP) technique. Routine paraffin sections were used. In lichen planus deposits of immunoglobulins were seen in and around epithelial cells, in colloid bodies, at epidermo-dermal junctions, and in some inflammatory cells. All cases examined for IgM and eight out of 13 cases examined for IgG were positive. The peripheral migrating epidermal cells were mostly negative. The application of the PAP technique to skin biopsy and the significance of the findings in lichen planus are discussed.