Increase in rosette-forming T cells with autologous human erythrocytes in lymphocytes of patients with tuberculosis by in vitro stimulation with purified protein derivative.

Lymphocytes of tuberculous patients activated in vitro with purified protein derivative of tuberculin (PPD) were examined for rosette formation with human autologous erythrocytes. The percentage of the rosette-forming cell (auto-RFC) was increased when pleural fluid lymphocytes of patients with tuberculous pleurisy and peripheral blood lymphocytes (PBL) from patients with tuberculosis or from tuberculin skin test positive healthy individuals were stimulated with PPD in vitro, whereas no increase of auto-RFC was observed in PBL from tuberculin skin test negative donors. Increased numbers of auto-RFC were shown to form rosettes with sheep erythrocytes but have no IgG Fc receptors on their surfaces. It was also shown that adherent cells were required for the PPD-induced increase of auto-RFC. Depletion of PPD-induced auto-RFC by the density gradient sedimentation technique led to a significant decrease in the degree of the proliferative response to gradient sedimentation technique let to a significant decrease in the degree of the proliferative response to PPD and the number of the auto-RFC after stimulation with PPD. These findings strongly suggest that PPD-induced auto-RFC represents the consequence of an immunological interaction between sensitized T lymphocytes and relevant antigen PPD, and reflects the PPD responsiveness of tuberculosis at the T cell level.