Predominant intraepithelial localization of primed T cells and immunoglobulin-producing lymphocytes in Graves' disease

It has been proposed that intrathyroid lymphocytes, localized in specific anatomical sites might have distinct, pathophysiologically relevant functions in Graves' disease. However, most studies of intrathyroidal lymphocytes were restricted to two lymphocyte locations and used semiquantitative methods. Therefore we used seven anatomically different lymphoid compartments to classify and evaluate by quantitative representative methods the total intrathyroidal lymphocytic infiltration and the staining indexes for immunoglobulin-producing plasmocytes and primed T cells (CD45RO), which provide maximum help to pokeweed mitogen-stimulated immunoglobulin synthesis in 36 thyroid glands from patients with Graves' disease. We found only 3.4% of all intrathyroidal lymphocytes intraepithelially. However, only intraepithelial lymphocytes showed a significantly higher staining index for primed T cells compared with several other compartments. There was also a high staining index for immunoglobulin-producing lymphocytes in this compartment. Kappa- and lambda-positive plasmocytes were found in a polyclonal distribution (kappa:lambda = 64.1: 35.9) in all compartments. This increased incidence of CD45RO-positive T lymphocytes and of immunoglobulin-producing lymphocytes among the intraepithelial lymphocytes suggests a distinct pathophysiological function of lymphocytes in peripolesis in Graves' disease. Furthermore, there is a polyclonal intrathyroidal immunoglobulin synthesis.