PHA stimulation of peripheral blood lymphocytes in oral lichen planus. Abnormality localized between interleukin-2 receptor ligand formation and gamma-interferon secretion.

Peripheral blood T cell function in five oral lichen planus (OLP) patients and five healthy controls was assessed using different activation parameters. Staining with monoclonal antibodies against interleukin-2 receptor and MHC locus II coded Ia antigen, 3H-thymidine incorporation and gamma-interferon secretion were determined in phytohaemagglutinin (PHA) stimulated peripheral blood mononuclear cell cultures at days 0, 1, 3 and 5. The peripheral blood T cell subsets and spontaneous MHC locus II antigen expression were similar in OLP patients and in controls whereas the spontaneous lymphocyte proliferation was lower in OLP patients than in controls (p less than 0.01). This may reflect a slight in vivo preactivation and its effect on lymphocyte recirculation. The PHA-induced expression of IL-2 receptor and T cell proliferation were similar in both groups whereas gamma-interferon secretion and MHC locus II antigen expression were low in OLP patients compared with controls (p less than 0.01). The results suggest a defect in OLP T cell activation disclosed by in vitro PHA stimulation and localized between IL-2 receptor ligand binding and gamma-interferon secretion.