Lymphocyte activation in oral lichen planus in situ.

The current study evaluated the activation of T-cell mediated cellular immune response in the oral lesions in lichen planus (OLP). Analysis was made of the ultramorphology, lymphocyte activation marker expression, DNA synthesis, and gamma-interferon production of the inflammatory cells in OLP lesions. According to these four different aspects of lymphocyte activation, only a minor fraction, 5% at the most, of all T-cells in situ were activated. This minor fraction, however, not the resting T-cells without these signs of activation, may decide the outcome of the local immune-inflammatory process in OLP. Of the inflammatory cells in situ, however, 81 +/- 5% were Ia positive. This finding may be the result of an Ia inducing capacity of the gamma-interferon produced locally by the activated T-cells.