Identification of activated T cells in sarcoidosis.

When peripheral blood lymphocytes are stimulated by mitogens or allogeneic cells, they acquire the capacity to form stable rosettes at 37 degrees C with sheep red blood cells, thereby identifying a population of activated T cells. In 7 consecutive patients with acute sarcoidosis, there was a significant (P less than 0.005) increase in the proportion and the total number of peripheral blood lymphocytes forming stable rosettes at 37 degrees C compared to age-matched normal control subjects (mean +/- SE, 12.6 +/- 3.0 versus 2.0 +/- 0.3 per cent, respectively). This occurred despite a significant decrease in the total number of lymphocytes (P less than 0.01) and T cells (P less than 0.001) in the peripheral blood in these same patients. Light and electron microscopic examination of sarcoid lymphocytes confirmed that cells forming stable rosettes at 37 degrees C were activated or atypical. Thus, in acute sarcoidosis, activated T cells are increased, whereas the total number of T cells is decreased in peripheral blood. This finding also posed certain technical problems in identifying B cells by surface immunoglobulin and complement receptors. Measures to overcome these difficulties are discussed. As determined by 2 independent tests of B cells (i.e., complement receptor and surface immunoglobulin), the number of circulating B cells was decreased.