Lymphocytic alveolitis, bronchoalveolar lavage viral load, and outcome in human immunodeficiency virus infection.

Lymphocytic alveolitis portends a poor prognosis in human immunodeficiency virus (HIV)-infected subjects. Because alveolar lymphocytes consist predominantly of HIV-specific CD8(+) cytotoxic T lymphocytes (CTL), they could represent an appropriate immune response to infected cells in the lung, and be a surrogate marker for a high pulmonary viral burden. We assessed long-term outcome in a cohort of asymptomatic HIV-infected subjects who underwent bronchoscopy between 1990 and 1993 and had bronchoalveolar lavage fluid (BALF) available for determination of viral load by reverse transcription-polymerase chain reaction. The ability to detect HIV in BALF increased with disease progression. Lymphocytic alveolitis, although present at all stages of HIV infection, was most pronounced in patients with middle stage disease. The HIV viral load as measured by bronchoalveolar lavage correlated with the percentage of alveolar lymphocytes in patients with peripheral blood CD4(+) cell counts above 200/microliter. Including patients with CD4(+) cell counts < 200/microliter weakened this correlation, possibly because of replacement of CD8(+) CTL by CD8(+) suppressor cells in advanced disease. Free virus in BALF was a stronger predictor of HIV disease progression than was lymphocytic alveolitis. These data suggest that lymphocytic alveolitis in HIV-infected subjects occurs in response to viral antigens in the lung and that the poor prognosis associated with lymphocytic alveolitis reflects a high pulmonary viral burden.

Production of interferon-gamma by lung lymphocytes in HIV-infected individuals.

A CD8(+) lymphocytic alveolitis occurs in up to 60% of asymptomatic human immunodeficiency virus (HIV)-infected individuals. Early in HIV infection, lymphocytes consist predominantly of cytotoxic T lymphocytes directed against HIV-infected targets. As HIV disease progresses, they are replaced by CD8(+)CD57(+) suppressor cells. Virus-specific cytotoxic T lymphocytes secrete interferon-gamma (IFN-gamma), an important cytokine in upregulating immune responses, primarily through macrophage activation. We examined the ability of lung and blood lymphocytes from HIV-positive patients at various stages of HIV infection to secrete IFN-gamma spontaneously and in response to phytohemagglutinin A. IFN-gamma production and secretion were determined with ELISA, Western blot, immunoprecipitation, and Northern blot techniques. Lung lymphocytes from HIV-infected individuals secreted large amounts of IFN-gamma. However, this ability was lost in patients with late-stage disease. Correlation between blood and lung lymphocyte IFN-gamma secretion was poor, suggesting regional differences in lymphocyte function. These data suggest that lung levels of IFN-gamma are high until late in HIV disease. These findings support the concept of administering exogenous IFN-gamma to patients with late-stage HIV disease and opportunistic infections.

Impaired IgG production in the lungs of HIV-infected individuals.

Human immunodeficiency virus (HIV)-infected individuals are at risk for pulmonary infections with encapsulated bacterial pathogens. This could reflect impaired production of opsonizing antibodies in the lower respiratory tract. We examined antibody production in the alveolar space by measuring immunoglobulin concentrations in bronchoalveolar lavage (BAL) of HIV-infected patients and normal volunteers and by assessing the ability of alveolar macrophages (AM) to induce immunoglobulin production in normal peripheral blood mononuclear cells (PBMC). BAL from HIV-infected patients contained significantly less IgG than normal BAL. IgA and IgM concentrations were similar in both groups. Normal AM supported IgG and IgA production in PBMC. While HIV AM could induce IgA production in PBMC, in no instance did they induce IgG secretion. HIV AM produced significantly more transforming growth factor-beta (TGF-beta), a factor known to suppress IgG production, than normal AM. Finally, TGF-beta antibodies blocked the inhibitory effect of HIV AM on normal IgG secretion without affecting IgA secretion. These findings demonstrate impaired production of opsonizing IgG in the alveolar space of HIV-infected subjects and implicate excess TGF-beta production by AM as the cause of this impairment.

Effect of human lung allograft alveolar macrophages on IgG production: immunoregulatory role of interleukin-10, transforming growth factor-beta, and interleukin-6.

Alveolar macrophages (AM) are crucial to initiating and maintaining local immune responses. The increased susceptibility to pulmonary infections in lung allograft recipients may be due to impaired AM function resulting in diminished cellular and humoral immunity. We have previously reported that control AM were potent stimulators of IgG production from allogeneic peripheral blood mononuclear cells (PBM) in a manner that was dependent on gamma-interferon (gamma IFN). The ability of allograft AM to induce IgG production is unknown. The purpose of the current study was to compare the ability of allograft and control AM to induce IgG production from allogeneic PBM. In contrast to control AM which induced a dose-dependent stimulation of IgG production from allogeneic PBM, allograft AM were highly suppressive of IgG production. The inhibition was not due to a lack of allograft AM stimulation of gamma IFN production from responding lymphocytes. Supernatants from allograft AM were highly suppressive of control AM-induced IgG production. Allograft AM produced greater quantities of interleukin (IL-10) than control AM while transforming growth factor-beta (TGF-beta) production from these cells was comparable. Blocking antibodies to IL-10 and TGF-beta reversed the inhibition of IgG production to 63% and 60% of control, respectively. In addition, the production of interleukin 6 (IL-6), a macrophage-derived cytokine crucial to the stimulation of IgG synthesis, was deficient in the allograft AM. Addition of IL-6 to allograft AM and allogeneic PBM co-cultures restored IgG synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced proliferation and IL-2 secretion by lung lymphocytes from HIV-infected subjects.

Human immunodeficiency virus (HIV)-positive patients frequently develop a CD3+/CD8+ cytotoxic T cell lymphocytic alveolitis. This could occur through in situ expansion of lung lymphocytes. We evaluated lung and blood lymphocyte proliferation in asymptomatic HIV-infected individuals by measuring spontaneous and cytokine-induced tritiated thymidine incorporation. Interleukin (IL)-2 and IL-4 secretion was determined with the use of enzyme-linked immunosorbent assay, Western blotting, and immunoprecipitation techniques. Spontaneous proliferation by lung lymphocytes from HIV-positive patients was significantly greater than that of normal volunteers. Proliferation was confined to the CD8+ lymphocyte subset. Over time, spontaneous proliferation declined unless autologous alveolar macrophages (AM) were added, suggesting AM were providing additional stimulatory signals to lung lymphocytes. Lung and blood lymphocytes proliferated in response to IL-2 but not IL-4. Lymphocytes in HIV-infected lung spontaneously produced and secreted more IL-2 than either normal lung lymphocytes or autologous blood lymphocytes. IL-4 production was not detectable in either group. These findings support the hypothesis that lymphocytic alveolitis in asymptomatic HIV-positive patients results from IL-2-dependent in situ proliferation of CD3+/CD8+ cytotoxic T cells.

Measurement of IL-6 inhibitory activity in cultured cell supernatants and lysates.

Interleukin-6 (IL-6) participates in a variety of cellular activities including regulation of immune and inflammatory responses. We have previously reported a discrepancy between bioactive and antigenic IL-6 secretion by lipopolysaccharide-stimulated alveolar macrophages (AMs) from smokers and have speculated that this may be due to cosecretion of an IL-6 inhibitor. In this study we further define our methods for measuring IL-6 inhibitory activity by testing the ability of serially diluted, cultured cell supernatants and lysates to suppress proliferation of an IL-6-dependent cell line, B9, to optimal concentrations of rIL-6. AM secretion of the inhibitory factor was optimal when AMs were stimulated with 1 micrograms/ml lipopolysaccharide (LPS). AMs from smokers secreted significantly greater amounts of this factor than AMs from nonsmokers. It was crucial to remove IL-6 from test samples on an IL-6 immunoaffinity column before analyzing for IL-6 inhibitory activity because (1) B9 cell proliferation could be suppressed by excess amounts of IL-6 in test supernatants and (2) excess rIL-6 added to the inhibitor assay reduced inhibitory activity. The latter finding suggested that IL-6 inhibitory activity was due to a competitive inhibitor of IL-6. This factor was shown to be specific for IL-6, because no inhibitory activity was seen on IL-2- or IL-4-dependent cell lines. Finally, we demonstrated that monocytes could also secrete an inhibitor of IL-6 bioactivity. However, secretion appeared to be less than that observed by AMs, suggesting that differentiation of monocytes into macrophages upregulated production of this factor.

Role of alveolar macrophage-T cell adherence in accessory cell function in human immunodeficiency virus-infected individuals.

Previous work has shown that alveolar macrophages (AM) from human immunodeficiency virus (HIV)-infected patients are superior accessory cells (AC) and secrete greater amounts of T cell-stimulatory cytokines than do normal AM. We now examine the role of AM-T cell adherence in AM AC function by examining the ability of beta 2 integrins and intercellular adhesion molecule-1 (ICAM-1) to block adherence and lymphoproliferation. Mitogen-induced (concanavalin A, pokeweed mitogen) adhesion and proliferation were studied in the presence and absence of mAb directed against beta 2 integrins and ICAM-1. AM from normal subjects and HIV-positive patients were used as AC, and normal T cells were used as responders. Normal and HIV AM bound equal numbers of T cells under similar conditions. Adherence was blocked by antibodies to beta 2 integrins and ICAM-1 in both groups. Con A-induced lymphoproliferation was positively correlated with adherence in normal volunteers. In contrast, greater Con A-induced AM-T cell adherence in HIV-positive patients was associated with worse AC function. Antibodies that impaired AM-T cell adherence completely inhibited AC function in both groups when added at the beginning of mitogen assays, indicating that initial contact was required. However, the addition of antibodies after 4 h inhibited lymphoproliferation less in HIV-infected individuals than in normal volunteers, suggesting that prolonged AM-T cell adherence was less important for optimal AC function in these patients. Using these and previous results, we present a model for AM AC function in normal volunteers and HIV-infected individuals.

Impaired alveolar macrophage accessory cell function and reduced incidence of lymphocytic alveolitis in HIV-infected patients who smoke.

OBJECTIVE: To determine the effects of smoking on alveolar macrophage (AM) accessory cell (AC) function and the incidence of lymphocytic alveolitis in asymptomatic HIV-infected individuals. METHODS: AM AC function in smoking and nonsmoking HIV-positive volunteers was measured in concanavalin A and pokeweed mitogen assays. Mitogen-induced AM-T-cell adherence was determined. AM cytokine secretion was analyzed by interleukin (IL)-6 bioassay and IL-1 enzyme-linked immunosorbent assay (ELISA). The incidence of lymphocytic alveolitis in both groups was determined. RESULTS: AM from smokers were significantly poorer AC than AM from nonsmokers. Though AM-T-cell adherence was unaffected by smoking, IL-1 and IL-6 secretion was significantly impaired. Lymphocytic alveolitis was significantly less common in HIV-infected smokers. CONCLUSION: Smoking reduces AM AC function in HIV-infected individuals, probably by impairing secretion of cytokines important in T-cell proliferation. This may explain the decreased incidence of lymphocytic alveolitis in HIV-infected people who smoke.

Cigarette smoking decreases bioactive interleukin-6 secretion by alveolar macrophages.

Studies suggest smokers have decreased alveolar macrophage (AM) accessory cell (AC) function and a reduced incidence of immune-mediated lung diseases such as sarcoidosis. Impaired AM secretion of cytokines important in T-cell immune responses could explain this observation. We investigated production and secretion of interleukin-1 (IL-1) and interleukin-6 (IL-6) in smokers and nonsmokers. Lipopolysaccharide-induced AM IL-1 secretion in smokers was significantly reduced compared with nonsmoker AM. However, intracellular IL-1 in smoker AM was higher than in nonsmokers, suggesting that reduced IL-1 secretion was due to impaired release rather than reduced production. Smoker AM secreted significantly less bioactive IL-6 measured in a bioassay compared with nonsmoker AM. Intracellular IL-6 was virtually undetectable in both groups. In some smokers IL-6 production determined by immunoprecipitation was reduced. However, as a group antigenic IL-6 secretion determined by enzyme-linked immunoabsorbent assay was similar in smokers and nonsmokers, suggesting that smoker AM may cosecrete an inhibitor of IL-6 bioactivity. Indeed, AM supernatants from smokers inhibited B9 proliferation in response to maximal recombinant IL-6 stimulation, whereas supernatants from nonsmokers did not. We conclude that AM from smokers secrete less cytokines important in T-cell proliferation than AM from nonsmokers and suggest that for IL-6 this impairment is related to both decreased production of antigenic protein as well as cosecretion of an IL-6 inhibitor.

Role of cytokines in alveolar macrophage accessory cell function in HIV-infected individuals.

Mononuclear phagocytes, including alveolar macrophages (AM), can be chronically infected with HIV and thus serve as a reservoir for the virus. Acting as AC during the generation of an immune response, HIV-infected mononuclear phagocytes can facilitate viral T cell infection by several mechanisms, including direct contact of T cells with HIV-infected macrophages as well as cytokine-induced up-regulation of latent T cell infection. Our laboratory has shown that AM from HIV-infected individuals have enhanced AC function compared to normal AM. In this study we explored AM production and secretion of IL-1 beta and IL-6, two cytokines critical for optimal AC function, in normal volunteers and HIV-infected patients. Cultured AM supernatants and lysates were generated in the presence and absence of LPS and standard mitogens. In initial mixing experiments HIV AM supernatants enhanced mitogen-induced T cell proliferation using normal AM as AC significantly more than normal AM supernatants, suggesting that HIV AM secreted more T cell stimulatory factors than normal AM. Neither group could enhance T cell proliferation induced by HIV AM suggesting these cells already secreted optimal levels of these factors. AM from HIV+ individuals produced and secreted more IL-1 beta (measured by ELISA) and IL-6 (measured in a B9 bioassay and by immunoprecipitation) than normal AM both spontaneously and in the presence of low LPS concentrations and mitogens. In some cases depleting HIV AM supernatants of IL-1 beta and IL-6 on immunoaffinity columns abrogated their enhancement properties indicating that these cytokines were important in the observed enhancement. However, in other patients different factors must also be involved as depletion of IL-1 beta and IL-6 in their AM supernatants had no effect on enhancement function. These results show that HIV AM secretory products are important in the enhanced AC function demonstrated by these cells. However, although augmented IL-1 beta and IL-6 secretion likely contribute significantly to this enhancement, other AC secretory factors and/or functions must also be involved.