Tuberculous Pleural Effusions: Evidence for Selective Presence of PPD-Specific T-Lymphocytes at Site of Inflammation in the Early Phase of the Infection

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Abstract
Patients with tuberculous pleural effusions may show cutaneous anergy to tuberculin purified-protein derivative (PPD). This phenomenon has been attributed either to preferential sequestration of antigen-specific T-lymphocytes to the pleural space or to the presence of suppressor monocytes in the blood. In 2 patients with primary tuberculous infection involving the pleura and with skin anergy to PPD, the in vitro proliferation of pleural and peripheral blood T-cells to PPD was evaluated. Although peripheral blood T-cells were not reactive, pleural T-cells showed a marked proliferative response to PPD. At least in the first patient, the lack of proliferation of circulating T-cells could not be related to the presence of suppressor monocytes. Interestingly, after 4 to 8 wk of specific chemotherapy, PPD skin test became positive and the blood T-lymphocytes responded in vitro to the same antigen. Pleural T-lymphocytes were used to generate long-term, PPD-specific T-cell lines and could be maintained in vitro for more than 3 months with repeated cycles of stimulation. The pleural and the blood T-lymphocytes and the T-cell lines were also characterized phenotypically: although the majority of the T-lymphocytes present in the pleural space after Mycobacterium tuberculosis infection were Leu-3-positive (helper T-cells), T-cell lines proliferating in response to PPD included high numbers of Leu-2-positive cells (suppressor/cytotoxic T-cells). These data suggest that early skin anergy in tuberculous pleuisy may be associated with sequestration of PPD-reactive T-lymphocytes in the pleural spaces involving both Leu-2 and Leu-3-positive T-cells.