Frequency of tuberculin-reactive T-lymphocytes in pleural fluid and blood from patients with tuberculous pleurisy.

A limiting dilution assay was used to determine the frequency of T-lymphocytes reactive to purified protein derivative of tuberculin (PPD). Pleural fluid from patients with tuberculous pleurisy showed higher frequencies of PPD-reactive T-lymphocytes than peripheral blood from the same patients or tuberculin-positive healthy control subjects. The mean frequencies were 1/2,204 T cells in pleural fluid from tuberculous pleurisy, 1/14,970 T cells in peripheral blood from the same patients, and 1/13,130 T cells in peripheral blood from healthy controls. The concentration of tuberculin-reactive lymphocytes in tuberculous pleural fluid could represent selective accumulation or in situ expansion of this population of cell.