EXPRESSION AND FUNCTION OF A CD3-LIKE MOLECULE ON NORMAL AND ABNORMALHUMAN PARATHYROID CELLS

Background. Normal and abnormal human parathyroid tissue express the T -lymphocyte protein. CD4, and parathyroid and lymphocyte cells show si milarities with respect to mechanisms of calcium permeability and regu lation of the cytoplasmic calcium concentration. Methods. Anti-Leu4, a monoclonal antibody recognizing the T-lymphocyte glycoprotein complex CD3, is used to immunohistochemically stain normal and abnormal human , parathyroid cells and to explore influences on the parathyroid hormo ne (PTH) secretion of enzymatically dispersed parathyroid cells. Resul ts. Parathyroid glands of patients with different forms of hyperparath yroidism displayed variable expression of the anti-CD3 reactive comple x. The stainings correlated both positively and inversely to immunorea ctivity for a previously defined calcium sensor, the decreased express ion of which may constitute a molecular basis for hyperparathyroidism. Incubation of parathyroid cells with the anti-Leu4 antibody inhibited PTH secretion and reduced its sensitivity to external calcium without influence on parathyroid cytoplasmic calcium concentration. Conclusio ns. The results suggest that-the human parathyroid cells express a CD3 -like molecule with the ability to interact in PTH release.