Ia-positive T lymphocytes in recently diagnosed idiopathic Addison's disease.

The Ia (DR, immune-associated) antigen is absent on normal circulating T lymphocytes, but present on activated T lymphocytes. Utilizing monoclonal antibody L243, the expression of this glycoprotein on circulating T lymphocytes was studied in five patients with recent-onset idiopathic Addison's disease, one patient with recent-onset adrenal hemorrhage, and nine patients with long-standing adrenal insufficiency (five with idiopathic Addison's disease and four after bilateral adrenalectomy for Cushing's disease). The patient with adrenal hemorrhage and the nine patients with long-standing adrenal insufficiency had percentages of circulating Ia-positive T cells within the normal range. All five patients with recent-onset idiopathic Addison's disease had an elevated percentage of circulating Ia-positive T cells (7 to 29 percent). The expression of Ia antigen on T cells in recent-onset idiopathic Addison's disease probably reflects immunologic activation, which may be of pathophysiologic importance.