T lymphocyte activation state in the minor salivary glands of patients with Sjögren's syndrome

Local lymphoplasmacytoid infiltration of the diseased exocrine glands is a cardinal sign of Sjögren's syndrome (SS). The state of T lymphocyte activation present in these local infiltrations was studied by three different techniques: determination of interleukin 2 (IL2) receptor (Tac) on cell surface membrane; autoradiography combined with immunoperoxidase staining of T cell epitopes; and electron microscopic analysis of the lymphoblast subclasses. Although 64 (SEM 4)% of the local inflammatory cells expressed Ia antigen, only 4 (SEM 1)% of them displayed the T cell activation antigen Tac. Autoradiography-immunoperoxidase double labelling showed that less than 1% of all T cells in situ were [3H]thymidine incorporating blasts. This finding suggests that although T lymphocyte is the dominant cell in situ, only a few of these cells have passed the G0/G1 interphase, and even fewer have been pushed to the S phase of the cell cycle by IL2. Transmission electron microscopy showed that few T blasts were present, even though there were many plasma cells. This result further confirms the impression that only a minor T cell subpopulation in situ is blast transformed despite the fact that many of the local T lymphocytes in the diseased salivary glands in SS are Ia positive.