Background Macrophage activation by cytokines provides only a partial explanation of antimycobacterial immunity in man. Because cytolytic T lymphocytes

SUMMARYThe cytolytic capacity of mycobacterial antigen-stimulated peripheral blood mononuclear cells, from healthy Mantoux-positive volunteers and from paiients with tuberculosis was investigated. Polyclonal T cell lines induced by 7 days of stimulation in vitro with PPD or a sonicate of Mycobacterium tubercutosis lysed both autologous macrophages and Epstein-Barr virus (EBV) transformed B cell lines which had been pulsed with mycobacterial antigens, to a greater extent than unpulsed target cells or target cells pulsed with an irrelevant antigen (strcptokinasc, streptodornase). The killing of mycobacterial antigen-pulsed macrophages and EBV-transformed B cell line targets was inhibited by monoclonal antibodies to MHC class II antigens but not by antibodies directed against MHC class I antigens. PPD-pulsed EBV-transformed lymphoblasloid cell lines (LCL) competitively inhibited the killing of mycobacterial antigen-pulsed macrophages, whereas natural killer (NK) sensitive K562 cells (with or without antigen pulsing) did not inhibit mycobacterial antigen-dependent cytolysis of macrophages. Patients with tuberculosis showed a spectrum of mycobacterial antigen-induced cytolytic capacity. Those with extensive tissue necrosis (e.g. cavitatory pulmonary tuberculosis or easeous. extrathoracic tuberculosis) had high levels while patients with disseminated (miliary) tuberculosis or disease refractory to treatment showed little evidence of mycobacterial antigen induced cytotoxicity. The ability of mycobacteriai antigenstimulated lymphoblasls to kill specific antigen-pulsed autologous macrophages was not significantly different between healthy donors and patients with tuberculosis. However, the 'mycobacterial antigen-specific" component of this cytolysis was significantly deficient iP<0-0\) in patients. We conclude that mycobacterial antigen-specific cytotoxic T cell responses may play a significant part in the immune response to mycobacterial infection.

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