Human immunodeficiency virus (HIV) is implicated in the development of AIDS (acquired immune deficiency syndrome). HIV infection leads to the generation of HIV-specific thymus-derived (T) lymphocytes in humans and apes. We describe an experimental system permitting the quantitative and systematic analysis of HIV-specific cytotoxic T lymphocytes (CTL). Functional, HIV-specific CTL are obtained by broncho-alveolar lavage (BAL) from the lungs of seropositive patients with lymphocytic alveolitis. These alveolar CTL: (1) recognize and kill HIV-infected alveolar macrophages in vitro under autologous, but not heterologous, conditions; (2) correspond to standard CTL as they express the CD3 and CD8 surface markers, but not the CD4 marker; and (3) are restricted by class I HLA transplantation antigens in their cytotoxic activities. We propose the hypothesis that interactions between HIV-specific CTL and infected macrophages induce major inflammatory reactions in seropositive patients.

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An avirulent and a virulent strain of Mycobacterium avium were selected on the basis of their growth patterns in human monocyte-derived macrophages. The virulent 7497 M. avium grew progressively in untreated macrophages, whereas the avirulent LR/149 M. avium was killed to a moderate extent by untreated human macrophages (50% of the original infectious inoculum killed 7 days after infection). We set out to investigate the possibility of modulating these growth patterns by cytokine treatment. Application of tumor necrosis factor (TNF) (100 U/ml) led to macrophages restricting significantly the growth of virulent M. avium 7497 (tenfold decrease at 7 days). TNF was also effective at modulating positively the interaction between avirulent LR/149 M. avium and macrophages inasmuch as TNF-treated cells killed 99% of infecting mycobacteria at 7 days. Granulocyte macrophage-colony stimulating factor (GM-CSF) (100-10,000 U/ml) treatment led to macrophages being as mycobacteriostatic for virulent 7497 M. avium as TNF-alpha-treated cells (i.e., tenfold reduction in growth). Treatment of macrophages with both GM-CSF and TNF-alpha was shown to have additive effects on bacteriostatic activity on M. avium. The mechanism of killing of avirulent M. avium by TNF-alpha was shown to be dependent on the generation of reactive nitrogen intermediates, as seen by inhibition of effector mechanisms by NG-monomethyl-arginine and arginase. Moreover, there was a correlation between NO2- generation and mycobactericidal activity of macrophages. Addition of superoxide dismutase reversed the killing of avirulent M. avium by untreated or TNF-treated macrophages. This abrogation was also apparent in chronic granulomatous disease (CGD) macrophages, which were inefficient at generating reactive oxygen intermediates. Moreover, macrophages from CGD patients killed avirulent M. avium as efficiently as cells from normal individuals. We conclude from these results that 1) GM-CSF and TNF-alpha, alone or in combination, increase effector functions of macrophages against virulent and avirulent strains of M. avium; 2) reactive nitrogen intermediates seem to be involved in this effector mechanism; and 3) superoxide dismutase protected M. avium against macrophage effector function, seemingly by protecting the bacteria against endogenous superoxide anion. The implications of these findings for host resistance to atypical mycobacteria are discussed.

The production of nitric oxide (NO) and other reactive nitrogen intermediates by cytokine-activated rodent cells is an important component of antimicrobial and/or antineoplastic activity of these cells. This pathway involves the oxidation of arginine to citrulline, with the concomitant release of NO by an inducible form of NO synthase (iNOS). Numerous cell types express iNOS after stimulation with bacterial products and/or cytokines. The role of NO and its derivatives in host resistance is a subject of intense investigation in mouse models of infections or neoplasia. Although human cells such as hepatocytes and endothelial cells have been shown to express an inducible NO synthase, the presence of such a pathway in human monocytes/macrophages has been questioned by many investigators and is a subject of great controversy. In this short review, we discuss some salient points of this debate.

Clusterin/apoJ is an intriguing gene frequently isolated by differential screening in laboratories from different areas of molecular biology, since it is overexpressed in numerous cases of degenerative diseases such as Alzheimer's disease and scrapie. While the dramatic increase of clusterin expression in injured tissues is well established, the molecular basis of the gene induction remains unclear. In this study, we have focused our attention on the only DNA region strictly conserved between clusterin gene proximal promoters from different vertebrate classes. We show that this 14-bp DNA element is specifically recognized by the HSF1 transcription factor and can mediate heat-shock-induced transcription in transient expression assays. Conversely, the avian clusterin proximal promoter, point-mutated at the level of this element, no longer transmits heat-shock activation. These findings provide a possible explanation for the high sensitivity of clusterin expression to environmental changes and allow the classification of clusterin as an extracellular version of heat-shock protein.