The proliferation of cells in the dermal infiltrate of lichen planus lesions.

Abstract

The proliferation of mononuclcar cells infiltrating the dermis in lichen planus lesions was studied in five untreated patients. A biopsy of a lesion was made in each patient. Thin slices of the specimens were incubated for 60 min in the presence of 3H thymidine (3HT), fixed and radioautographed. The mean value of the 3HT labelling index (±SE) was 2.87±0.14%. This labelling index (LI) is relatively high; it is not statistically different from the LI encountered in the dermal infiltrate of allergic contact dermatitis (P>0.45), but is three to four times higher than in psoriasis or irritant dermatitis. The proliferative cells are most probably lymphoblasts. A biopsy of another lichen planus lesion was made in two of the five patients 60 min after a local injection of 10 μCi of 3HT. Imprints of lesions were treated histochemically for Naphthol AS-D acetate esterase(s) identification, a useful method for distinguishing monocytes (many cytoplasmic granules) and lymphocytes (few if any granules). The imprints were then radioautographed. No 3HT-labelled cells contained more than one or two cytoplasmic granules, which suggests that they are of lymphocytic origin. The biological significance of this lymphoblastic proliferation still remains hypothetical.