Immunological activity of a 14-kilodalton recombinant protein of Mycobacterium tuberculosis H37Rv.

A 14-kilodalton peptide antigen from Mycobacterium tuberculosis was isolated from an Escherichia coli lambda gt 11 recombinant DNA clone and was identified by Western blotting (immunoblotting) with monoclonal antibody TB68. Immunization of mice and guinea pigs with the recombinant peptide (rTB68) induced in vitro lymphoproliferative responses in draining lymph node lymphocyte cultures as well as in vivo delayed-type hypersensitivity reactions. Moreover, rTB68 was found both to induce and to cross-react with Mycobacterium leprae immune lymphocytes, but did not generate protective effects against live M. leprae challenge in mice. These findings showed that a 14-kilodalton peptide which has been characterized as specific for M. tuberculosis on the basis of B-cell recognition was capable of generating cell-mediated immune responses and moreover contained T-cell epitopes which were cross-reactive with M. leprae antigens.

Mechanism of immunosuppression in leprosy--macrophage membrane alterations.

L-Lysate induced macrophage membrane alteration was studied using 3 membrane markers: (i) Fc receptor, (ii) Concanavalin A (Con A) receptor, and (iii) M. leprae adherence to macrophage membrane. The data indicate that L-lysate induces membrane perturbation of normal macrophages. The alteration can be reversed with trypsin and colchicine. Membrane alteration observed may lead to defective macrophage participation in a cell-mediated immune reaction.

Mechanism of immunosuppression in leprosy: presence of suppressor factor(s) from macrophages of lepromatous patients.

Human peripheral blood mononuclear cell proliferation induced by Mycobacterium leprae could be inhibited by the suppressor factor in the lysate of the macrophages of lepromatous leprosy patients. Macrophages from normal subjects and tuberculoid patients did not show production of a suppressor factor. Inhibition occurred only when the factor was present in the initial stages of lymphocyte culture. The factor is heat stable and nondialyzable. Proliferation induced by some mycobacteria and concanavalin A could also be blocked by the factor. Interestingly, blastogenic response by a few other antigens and phytohemagglutinin could not be inhibited by the suppressor factor. Mononuclear cells pretreated with such lysate from lepromatous macrophages for 24 h could induce suppressive activity in the cells in vitro in an autologous system. Treatment of these cells with carbonyl iron after the induction phase, to remove phagocytic cells, did not abolish their suppressive activity. The lepromatous macrophage lysate also generated suppressive activity in a T-lymphocyte-enriched population of normal subjects. These studies are interpreted to indicate that immunosuppression in lepromatous patients is produced by both macrophages and T lymphocytes. The exact phase in which either of these cells acts as a suppressor may be different. Specific suppression by macrophages to M. leprae can be an early event, and nonspecific suppression by T lymphocytes may be a later event in the course of lepromatous leprosy.

Role of macrophages in defective cell mediated immunity in lepromatous leprosy. I. Factor(s) from macrophages affecting protein synthesis and lymphocyte transformation.

Macrophages from lepromatous leprosy patients specifically show reduced protein synthesis in the presence of M. leprae. They also produce, as a result of interaction with M. leprae, factor(s) that reduce protein synthesis in normal macrophages as well as block lymphocyte transformation in normal leukocyte cultures in the presence of M. leprae as the antigen. These observations implicate a defective macrophage system in lepromatous leprosy patients.

Role of macrophages in defective cell mediated immunity in lepromatous leprosy. II. Macrophage and lymphocyte interaction.

Macrophages from lepromatous patients after phagocytosis of M. leprae showed alteration in their surface property as determined by their ability to express Fc receptors. The same macrophages without intracellular M. leprae show normal Fc receptors. The lepromatous macrophages also show very poor interaction with lymphocytes in the presence of M. leprae while they are able to interact with lymphocytes when exposed to other antigens. These observations along with earlier ones on macrophage defects have indicated a probable reason for defective cell mediated immunity (CMI) in lepromatous leprosy patients. There appears to be a defective macrophage population in lepromatous patients that is unable to process M. leprae antigens and initiate the CMI response.

The role of macrophages in leprosy as studied by protein synthesis of macrophages from resistant and susceptible hosts--a mouse and human study.

3H-leucine uptake by macrophages from swiss white and C57BL mice before and after M. leprae infection was studied. A depression in 3H-leucine uptake after infection was observed only in swiss white mice. 3H-leucine uptake was also studied in blood derived macrophages from normals, and LL and TT patients. A depression was obtained in 3H-leucine uptake after M. leprae infection in macrophages from LL patients.