IMMUNOLOGICAL STUDY ON HUMAN TUBERCULOSIS AT THE CELLULAR LEVEL

Abstract

It was found that there were two different subsets of thymus derived T lymphocytes when lympho cytes from patients with tuberculosis were stimulated in vitro with tuberculin purified protein derivative, PPD. The one was IgG Fc-receptor bearing T cells (T_G) and the other was rosette forming T cells with autologous erythrocytes. Both of which are supposed to play an important role not only in the induction of tuberculin hypersensitivity but also in immunity to tuberculosis.
1) Increase in IgG Fc-receptor bearing T cells (T_G) in PBL of tuberculous patients by the in vitro stimulation with PPD
A mixed rosette technique with sheep erythrocytes and chicken erythrocytes coated with heat aggregated human IgG was employed to identify human peripheral blood T lymphocytes bearing IgG Fc-receptor (T_G). When peripheral blood lymphocytes (PBL) from patients with advanced, refrac tory tuberculosis were stimulated in vitro with PPD, increase in the number of T_G cells was observed, whereas no such T_G cells were developed in PBL from newly diagnosed tuberculous patients after the stimulation with PPD. T^G cells isolated from the tuberculin skin test positive individual by the method of velocity sedimentation suppressed PPD-induced proliferative response of autologous PBL, as well as the pokeweed mitogen-induced IgG synthesis by B cells.
2) PPD-stimulated development in tuberculosis of T cells bearing receptors for autologous erythrocytes Tuberculous human lymphocytes activated in vitro with tuberculin PPD were examined for rosette formation with autologous erythrocytes. The autorosette forming cell (auto-RFC) levels were strongly enhanced when pleural fluid lymphocytes and, to a lesser extent, PBL of the patients with tuberculosis were stimulated in vitro with PPD, whereas no increase in auto-RFC was observed in PBL from tuberculin skin test negative healthy individuals. These auto-RFC developed were shown to rosette with sheep erythrocytes and, therefore, belong to a T cell subset. It was also shown that adherent cells were required for the development of auto-RFC by the stimulation with PPD. Deple tion of PPD-stimulated auto-RFC by the velocity sedimentation technique led to a significant de crease in PPD reactivity assessed by the proliferation or auto-RFC formation.led to a significant de crease in PPD reactivity assessed by the proliferation or auto-RFC formation.