PHA and PPD reactivity of lymphocytes in pleural effusions.

The functional properties of lymphocytes in pleural fluid were studied in 23 patients admitted to the hospital for the diagnostic evaluation of a unilateral or bilateral pleural effusion. The in vitro reactivities of the patients' pleural fluid lymphocytes and peripheral blood lymphocytes to phytohemagglutinin (PHA) and to purified protein derivative (PPD) were compared. In most patients with pleural effusion, the function of pleural fluid lymphocytes was intact and comparable to that of lymphocytes from peripheral blood. The PHA- and PPD-stimulated 3H-thymidine incorporation by peripheral blood lymphocytes did not differ significantly from that by pleural fluid lymphocytes in any of the patient groups. Similarly, the comparison of PHA- and PPD-stimulated 3H-thymidine uptake by peripheral blood or pleural fluid lymphocytes from patients with pleural effusions of various causes revealed no significant differences. In vitro reactivity to PPD by peripheral blood and pleural fluid lymphocytes correlated positively with the in vivo intradermal reactivity to PPD.